We shall give a brief description of the appearance of the principal elementary bodies upon being fused with charcoal. This plan is that deemed the most conducive to the progress of the student, by Berzelius, Plattner, and Sherer. Experience has taught us that this method is the most efficient that could have been devised as an initiatory exercise for the student, ere he commences a more concise and methodical method of analysis. In these reactions upon charcoal, we shall follow nearly the language of Plattner and Sherer.

SELENIUM is not difficult of fusion, and gives off brown fumes in either the oxidation or reduction flame. The deposit upon the charcoal is of a steel-grey color, with a slightly metallic lustre. The deposit however that fuses outside of this steel-grey one is of a dull violet color, shading off to a light brown. Under the flame of oxidation this deposit is easily driven from one portion of the charcoal to another, while the application of the reducing flame volatilizes it with the evolution of a beautiful blue light. The characteristic odor of decayed horse-radish distinguishes the volatilization of this metal.

TELLURIUM.—This metal fuses with the greatest readiness, and is reduced to vapor under both flames with fumes, and coats the charcoal with a deposit of tellurous acid. This deposit is white near the centre, and is of a dark yellow near the edges. It may be driven from place to place by the flame of oxidation, while that of reduction volatilizes it with a green flame. If there be a mixture of selenium present, then the color of the flame is bluish-green.

ARSENIC.—This metal is volatilized without fusing, and covers the charcoal both in the oxidizing and reducing flames with a deposit of arsenious acid. This coating is white in the centre, and grey towards the edges, and is found some distance from the assay. By the most gentle application of the flame, it is immediately volatilized, and if touched for a moment with the reducing flame, it disappears, tinging the flame pale blue. During volatilization a strong garlic odor is distinctly perceptible, very characteristic of arsenic, and by which its presence in any compound may be immediately recognized.

ANTIMONY.—This metal fuses readily, and coats the charcoal under both flames with antimonious acid. This incrustation is of a white color where thick, but of a bluish tint where it is thin, and is found nearer to the assay than that of arsenic. When greatly heated by the flame of oxidation, it is driven from place to place without coloring the flame, but when volatilized by the flame of reduction, it tinges the flame blue. As antimonious acid is not so volatile as arsenious acid, they may thus be easily distinguished from one another.

When metallic antimony is fused upon charcoal, and the metallic bead raised to a red heat, if the blast be suspended, the fluid bead remains for some time at this temperature, giving off opaque white fumes, which are at first deposited on the surrounding charcoal, and then upon the bead itself, covering it with white, pearly crystals. The phenomenon is dependent upon the fact, that the heated button of antimony, in absorbing oxygen from the air, developes sufficient heat to maintain the metal in a fluid state, until it becomes entirely covered with crystals of antimonious acid so formed.

BISMUTH.—This metal fuses with ease, and under both flames covers the charcoal with a coating of oxide, which, while hot, is of an orange-yellow color, and after cooling, of a lemon-yellow color, passing, at the edges, into a bluish white. This white coating consists of the carbonate of bismuth. The sublimate from bismuth is formed at a less distance from the assay than is the case with antimony. It may be driven from place to place by the application of either flame; but in so doing, the oxide is first reduced by the heated charcoal, and the metallic bismuth so formed is volatilized and reoxidized. The flame is uncolored.

LEAD.—This metal readily fuses under either flame, and incrusts the charcoal with oxide at about the same distance from the assay as is the case with bismuth. The oxide is, while hot, of a dark lemon-yellow color, but upon cooling, becomes of a sulphur yellow. The carbonate which is formed upon the charcoal, beyond the oxide, is of a bluish-white color. If the yellow incrustation of the oxide be heated with the flame of oxidation, it disappears, undergoing changes similar to those of bismuth above mentioned. Under the flame of reduction, it, however, disappears, tinging the flame blue.

CADMIUM.—This metal fuses with ease, and, in the flame of oxidation, takes fire, and burns with a deep yellow color, giving off brown fumes, which coat the charcoal, to within a small distance of the assay, with oxide of cadmium. This coating exhibits its characteristic reddish-brown color most clearly when cold. Where the coating is very thin, it passes to an orange color. As oxide of cadmium is easily reduced, and the metal very volatile, the coating of oxide may be driven from place to place by the application of either flame, to neither of which does it impart any color. Around the deposit of oxide, the charcoal has occasionally a variegated tarnish.

ZINC.—This metal fuses with ease, and takes fire in the flame of oxidation, burning with a brilliant greenish-white light, and forming thick white fumes of oxide of zinc, which coat the charcoal round the assay. This coating is yellow while hot, but when perfectly cooled, becomes white. If heated with the flame of oxidation, it shines brilliantly, but is not volatilized, since the heated charcoal is, under these circumstances, insufficient to effect its reduction. Even under the reducing flame, it disappears very slowly.

TIN.—This metal fuses readily, and, in the flame of oxidation, becomes covered with oxide, which, by a strong blast, may be easily blown off. In the reducing flame, the fused metal assumes a white surface, and the charcoal becomes covered with oxide. This oxide is of a pale yellow color while hot, and is quite brilliant when the flame of oxidation is directed upon it. After cooling, it becomes white. It is found immediately around the assay, and cannot be volatilized by the application of either flame.

MOLYBDENUM.—This metal, in powder, is infusible before the blowpipe. If heated in the outer flame, it becomes gradually oxidized, and incrusts the charcoal, at a small distance from the assay, with molybdic acid, which, near the assay, forms transparent crystalline scales, and is elsewhere deposited as a fine powder. The incrustation, while hot, is of a yellow color, but becomes white after cooling. It may be volatilized by heating with either flame, and leaves the surface of the charcoal, when perfectly cooled, of a dark-red copper color, with a metallic lustre, due to the oxide of molybdenum, which has been formed by the reducing action of the charcoal upon the molybdic acid. In the reducing flame, metallic molybdenum remains unchanged.

SILVER.—This metal, when fused alone, and kept in this state for some time, under a strong oxidizing flame, covers the charcoal with a thin film of dark reddish-brown oxide. If the silver be alloyed with lead, a yellow incrustation of the oxide of that metal is first formed, and afterwards, as the silver becomes more pure, a dark red deposit is formed on the charcoal beyond. If the silver contains a small quantity of antimony, a white incrustation of antimonious acid is formed, which becomes red on the surface if the blast be continued. And if lead and antimony are both present in the silver, after the greater part of these metals have been volatilized, a beautiful crimson incrustation is produced upon the charcoal. This result is sometimes obtained in fusing rich silver ores on charcoal.

SULPHIDES, CHLORIDES, IODIDES, AND BROMIDES.

In blowpipe experiments, it rarely occurs that we have to deal with pure metals, which, if not absolutely non-volatile, are recognized by the incrustation they form upon charcoal. Some compound substances, when heated upon charcoal, form white incrustations, resembling that formed by antimony, and which, when heated, may, in like manner, be driven from place to place. Among these are certain sulphides, as sulphide of potassium, and sulphide of sodium, which are formed by the action of the reducing flame upon the sulphates of potassa and soda, and are, when volatilized, reconverted into those sulphates, and as such deposited on the charcoal. No incrustation is, however, formed, until the whole of the alkaline sulphate has been absorbed into the charcoal, and has parted with its oxygen. As sulphide of potassium is more volatile than sulphide of sodium, an incrustation is formed from the former sooner than from the latter of these salts, and is considerably thicker in the former case. If the potash incrustation be touched with the reducing flame, it disappears with a violet-colored flame; and if a soda incrustation be treated in like manner, an orange-yellow flame is produced.

Sulphide of lithium, formed by heating the sulphate in the reducing flame, is volatilized in similar manner by a strong blast, although less readily than the sulphide of sodium. It affords a greyish white film, which disappears with a crimson flame when submitted to the reducing flame.

Besides the above, the sulphides of bismuth and lead give, when heated in either flame, two different incrustations, of which the more volatile is of a white color, and consists in the one case of sulphate of lead, and in the other of sulphate of bismuth. If either of these be heated under the reducing flame, it disappears in the former case with a bluish flame, in the latter unaccompanied by any visible flame. The incrustation formed nearest to the assay consists of the oxide of lead or bismuth, and is easily recognized by its color when hot and after cooling. There are many other metallic sulphides, which, when heated by the blowpipe flame, cover the charcoal with a white incrustation, as sulphide of antimony, sulphide of zinc, and sulphide of tin. In all these cases, however, the incrustation consists of the metallic oxide alone, and either volatilizes or remains unchanged, when submitted to the oxidizing flame.

Of the metallic chlorides there are many which, when heated on charcoal with the blowpipe flame, are volatilized and redeposited as a white incrustation. Among these are the chlorides of potassium, sodium, and lithium, which volatilize and cover the charcoal immediately around the assay with a thin white film, after they have been fused and absorbed into the charcoal, chloride of potassium forms the thickest deposit, and chloride of lithium the thinnest, the latter being moreover of a greyish-white color. The chlorides of ammonium, mercury, and antimony volatilize without fusing.

The chlorides of zinc, cadmium, lead, bismuth, and tin first fuse and then cover the charcoal with two different incrustations, one of which is a white volatile chloride, and the other a less volatile oxide of the metal.

Some of the incrustations formed by metallic chlorides disappear with a colored flame when heated with the reducing flame; thus chloride of potassium affords a violet flame, chloride of sodium an orange one, chloride of lithium a crimson flame, and chloride of lead a blue one. The other metals mentioned above volatilize without coloring the flame.

The chloride of copper fuses and colors the flame of a beautiful blue. Moreover, if a continuous blast be directed upon the salt, a part of it is driven off in the form of white fumes which smell strongly of chlorine, and the charcoal is covered with incrustations of three different colors. That which is formed nearest to the assay is of a dark grey color, the next, a dark yellow passing into brown, and the most distant of a bluish white color. If this incrustation be heated under the reducing flame, it disappears with a blue flame.

Metallic iodides and bromides behave upon charcoal in a similar manner to the chlorides. Those principally deserving of mention are the bromides and iodides of potassium and sodium. These fuse upon charcoal, are absorbed into its pores, and volatilize in the form of white fumes, which are deposited upon the charcoal at some distance from the assay. When the saline films so formed are submitted to the reducing flame, they disappear, coloring the flame in the same manner as the corresponding chlorides.

4. EXAMINATIONS IN THE PLATINUM FORCEPS.

Before the student attempts to make an examination in the platinum forceps or tongs, he should first ascertain whether or not it will act upon the platinum. If the substance to be examined shall act chemically upon the platinum, then it should be examined on the charcoal, and the color of the flame ascertained as rigidly as possible. The following list of substances produce the color attached to them.

A. VIOLET.

Potash, and all its compounds, with the exception of the phosphate and the borate, tinge the color of the flame violet.

B. BLUE.

Chloride of copper, Intense blue. Lead, Pale clear blue. Bromide of copper, Bluish green. Antimony, Bluish green. Selenium, Blue. Arsenic, English green.

C. GREEN.

Ammonia, Dark green. Boracic acid, Dark green. Copper, Dark green. Tellurium, Dark green. Zinc, Light green. Baryta Apple green. Phosphoric acid, Pale green. Molybdic acid, Apple green. Telluric acid, Light green.

D. YELLOW.

Soda, Intense yellow. Water, Feeble yellow.

E. RED.

Strontia, Intense crimson. Lithia, Purplish red. Potash, Violet red. Lime, Purplish red.

The student may often be deceived in regard to the colors: for instance, if a small splinter of almost any mineral be held at the point of the flame of oxidation, it will impart a very slight yellow to the flame. This is caused, doubtless, by the water contained in the mineral. If the piece of platinum wire is used, and it should be wet with the saliva, as is frequently done by the student, then the small quantity of soda existing in that fluid will color the flame of a light yellow hue.

A. THE VIOLET COLOR.

The salts of potash, with the exception of the borate and the phosphate, color the flame of a rich violet hue. This color is best discovered in the outer flame of the blowpipe, as is the case with all the other colors. The flame should be a small one, with a lamp having a small wick, while the orifice of the blowpipe must be quite small. These experiments should likewise be made in a dark room, so that the colors may be discerned with the greatest ease. In investigating with potash for the discernment of color, it should be borne in mind that the least quantity of soda will entirely destroy the violet color of the potash, by the substitution of its own strong yellow color. If there be not more than the two hundredth part of soda, the violet reaction of the potash will be destroyed. This is likewise the case with the presence of lithia, for its peculiar red color will destroy the violet of the potash. Therefore in making investigations with the silicates which contain potash, the violet color of the latter can only be discerned when they are free from soda and lithia.

B. THE BLUE COLOR.

(a.) The Chloride of Copper.—Any of the chlorides produce a blue color in the blowpipe flame, or any salt which contains chlorine will show the blue tint, as the color in this case is referable to the chlorine itself. There are, however, some chlorides which, in consequence of the peculiar reactions of their bases, will not produce the blue color, although in these cases the blue of the chlorine will be very likely to blend itself with the color produced by the base. The chloride of copper communicates an intense blue to the flame, when fused on the platinum wire. If the heat be continued until the chlorine is driven off, then the greenish hue of the oxide of copper will be discerned.

(b.) Lead.—Metallic lead communicates to the flame a pale blue color. The oxide reacts in the same manner. The lead-salts, whose acids do not interfere with the color, impart also a fine blue to the flame, either in the platina forceps, or the crooked wire.

(c.) Bromide of Copper.—This salt colors the flame of a bluish-green color, but when the bromine is driven off, then we have the green of the oxide of copper.

(d.) Antimony.—This metal imparts a blue color to the blowpipe flame, but if the metal is in too small a quantity, then the color is a brilliant white. If antimony is fused on charcoal, the fused metal gives a blue color. The white sublimate which surrounds the fused metal, being subjected to the flame of oxidation, disappears from the charcoal with a bluish-green color.

(e.) Selenium.—If fused in the flame of oxidation, it imparts to the flame a deep blue color. The incrustation upon charcoal gives to the flame the same rich color.

(f.) Arsenic.—The arseniates and metallic arsenic itself impart to the blowpipe flame a fine blue color, provided that there is no other body present which may have a tendency to color the flame with its characteristic hue. The sublimate of arsenious acid which surrounds the assay, will give the same blue flame, when dissipated by the oxidation flame. The platinum forceps will answer for the exhibition of the color of arsenic, even though the salts be arseniates, whose bases possess the property of imparting their peculiar color to the flame, such as the arseniate of lime.

C. THE GREEN COLOR.

(a.) Ammonia.—The salts of ammonia, when heated before the blowpipe, and just upon the point of disappearing, impart to the flame a feeble though dark green color. This color, however, can only be discerned in a dark room.

(_b._) _Boracic Acid._—If any one of the borates is mixed with two parts of a flux composed of one part of pulverized fluorspar, and four and a half parts of bisulphate of potash, and after being melted, is put upon the coil of a platinum wire, and held at the point of the blue flame, soon after fusion takes place a dark green color is discerned, but it is not of long duration. The above process is that recommended by Dr. Turner. The green color of the borates may be readily seen by dipping them, previously moistened with sulphuric acid, into the upper part of the blue flame, when the color can be readily discerned. If soda be present, then the rich green of the boracic acid is marred by the yellow of the soda. Borax, or the biborate of soda (NaO, 2BO_{3}) may be used for this latter reaction, but if it be moistened with sulphuric acid, the green of the boracic acid can then be seen. If the borates, or minerals which contain boracic acid, are fused on charcoal with carbonate of potash, then moistened with sulphuric acid and alcohol, then the bright green of the boracic acid is produced, even if the mineral contains but a minute portion of the boracic acid.

(c.) Copper. Nearly all the ores of copper and its salts, give a bright green color to the blowpipe flame. Metallic copper likewise colors the flame green, being first oxidized. If iodine, chlorine, and bromine are present, the flame is considerably modified, but the former at least intensifies the color. Many ores containing copper also color the flame green, but the internal portion is of a bright blue color if the compound contains lead, the latter color being due to the lead. The native sulphide and carbonate of copper should be moistened with sulphuric acid, while the former should be previously roasted. If hydrochloric acid is used for moistening the salts, then the rich green given by that moistened with the sulphuric acid is changed to a blue, being thus modified by the chlorine of the acid. Silicates containing copper, if heated in the flame in the platinum forceps, impart a rich green color to the outer flame. In fact, if any substance containing copper be submitted to the blowpipe flame, it will tinge it green, provided there be no other substance present to impart its own color to the flame, and thus modify or mar that of the copper.

(d.) Tellurium.—If the flame of reduction is directed upon the oxide of tellurium placed upon charcoal, a green color is imparted to it. If the telluric acid be placed upon platinum wire in the reduction flame, the oxidation flame is colored green. Or if the sublimate be dissipated by the flame of oxidation, it gives a green color. If selenium be present, the green color is changed to a blue.

(e.) Zinc.—The oxide of zinc, when strongly heated, gives a blue flame. This is especially the case in the reducing flame. The flame is a small one, however, and not very characteristic, as with certain preparations of zinc the blue color is changed to a bright white. The soluble salts of zinc give no blue color.

(f.) Baryta.—The soluble salts of baryta, moistened, and then submitted to the reduction flame, produce a green color. The salt should be moistened, when the color will be strongly marked in the outer flame. The insoluble salts do not produce so vivid a color as the soluble salts, and they are brighter when they have previously been moistened. The carbonate does not give a strong color, but the acetate does, so long as it is not allowed to turn to a carbonate. The chloride, when fused on the platinum wire, in the point of the reduction flame, imparts a fine green color to the oxidation flame. This tint changes finally to a faint dirty green color. The sulphate of baryta colors the flame green when heated at the point of the reduction flame. But neither the sulphate, carbonate, nor, in fact, any other salt of baryta, gives such a fine green color as the chloride. The presence of lime does interfere with the reaction of baryta, but still does not destroy its color.

(g.) Phosphoric Acid.—The phosphates give a green color to the oxidation flame, especially when they are moistened with sulphuric acid. This is best shown with the platinum forceps. The green of phosphoric, or the phosphates, is much less intense than that of the borates or boracic acid, but yet the reaction is a certain one, and is susceptible of considerable delicacy, either with the forceps, or still better upon platinum wire. Sulphuric acid is a great aid to the development of the color, especially if other salts be present which would be liable to hide the color of the phosphoric acid. In this reaction with phosphates, the water should be expelled from them previous to melting them with sulphuric acid. They should likewise be pulverized. Should soda be present it will only exhibit its peculiar color after the phosphoric acid shall have been expelled; therefore, the green color of the phosphoric acid should be looked for immediately upon submitting the phosphate to heat.

(h.) Molybdic Acid.—If this acid or the oxide of molybdenum be exposed upon a platinum wire to the point of the reduction flame, a bright green color is communicated to the flame of oxidation. Take a small piece of the native sulphide of molybdenum, and expose it in the platinum tongs to the flame referred to above, when the green color characteristic of this metal will be exhibited.

(i.) Telluric Acid.—If the flame of reduction is directed upon a small piece of the oxide of tellurium placed upon charcoal, a bright green color is produced. Or if telluric acid be submitted to the reduction flame upon the loop of a platinum wire, it communicates to the outer flame the bright green of tellurium. If the sublimate found upon the charcoal in the first experiment be submitted to the blowpipe flame, the green color of tellurium is produced while the sublimate is volatilized. If selenium be present the green color is changed to a deep blue one.

D. YELLOW.

The salts of soda all give a bright yellow color when heated in the platinum loop in the reduction flame. This color is very persistent, and will destroy the color of almost any other substance. Every mineral of which soda is a constituent, give this bright orange-yellow reaction. Even the silicate of soda itself imparts to the flame of oxidation the characteristic yellow of soda.

E. RED.

(a.) Strontia.—Moisten a small piece of the chloride of strontium, put it in the platinum forceps and submit it to the flame of reduction, when the outer flame will become colored of an intense red. If the salt of strontia should be a soluble one, the reaction is of a deeper color than if an insoluble salt is used, while the color is of a deeper crimson if the salt is moistened. If the salt be a soluble one, it should be moistened and dipped into the flame, while if it be an insoluble salt, it should be kept dry and exposed beyond the point of the flame. The carbonate of strontia should be moistened with hydrochloric acid instead of water, by which its color similates that of the chloride of strontium when moistened with water. In consequence of the decided red color which strontia communicates to flame, it is used by pyrotechnists for the purpose of making their "crimson fire."

(b.) Lithia.—The color of the flame of lithia is slightly inclined to purple. The chloride, when placed in the platinum loop, gives to the outer flame a bright red color, sometimes with a slight tinge of purple. Potash does not prevent this reaction, although it may modify it to violet; but the decided color of soda changes the red of lithia to an orange color. If much soda be present, the color of the lithia is lost entirely. The color of the chloride of lithium may be distinctly produced before the point of the blue flame, and its durability may be the means of determining it from that of lithium, as the latter, under the same conditions, is quite evanescent. The minerals which contain lithia, frequently contain soda, and thus the latter destroys the color of the former.

(c.) Potash.—The salts of potash, if the acid does not interfere, give a purplish-red color before the blowpipe; but as the color is more discernibly a purple, we have classed it under that color.

(d.) Lime.—The color of the flame of lime does not greatly differ from that of strontia, with the exception that it is not so decided. Arragonite and calcareous spar, moistened with hydrochloric acid, and tried as directed for strontia, produce a red light, not unlike that of strontia. The chloride of calcium gives a red tinge, but not nearly so decided as the chloride of strontium. The carbonate of lime will produce a yellowish flame for a while, until the carbonic acid is driven off, when the red color of the lime may be discerned.

If the borate or phosphate of lime be used, the green color of the acids predominates over the red of the lime. Baryta also destroys the red color of the lime, by mixing its green color with it. There is but one silicate of lime which colors the flame red, it is the variety termed tabular spar.

5. EXAMINATIONS IN THE BORAX BEAD.

In order to examine a substance in borax, the loop of the platinum wire should, after being thoroughly cleaned, and heated to redness, be quickly dipped into the powdered borax, and then quickly transferred to the flame of oxidation, and there fused. If the bead is not large enough to fill the loop of the wire, it must be subjected again to the same process. By examining the bead, both when hot and cold, by holding it up against the light, it can be soon ascertained whether it is free from dirt by the transparency, or the want of it, of the bead.

In order to make the examination of a substance, the bead should be melted and pressed against it, when enough will adhere to answer the purpose. This powder should then be fused in the oxidation flame until it mixes with, and is thoroughly dissolved by the borax bead.

The principal objects to be determined now are: the color of the borax bead, both when heated and when cooled; also the rapidity with which the substance dissolves in the bead, and if any gas is eliminated.

If the color of the bead is the object desired, the quantity of the substance employed must be very small, else the bead will be so deeply colored, as in some cases to appear almost opaque, as, for instance, in that of cobalt. Should this be the case, then, while the bead is still red hot, it should be pressed flat with the forceps; or it may, while soft, be pulled out to a thin thread, whereby the color can be distinctly discovered.

Some bodies, when heated in the borax bead, present a clear bead both while hot and cold; but if the bead be heated with the intermittent flame, or in the flame of reduction, it becomes opalescent, opaque or milk-white. The alkaline earths are instances of this kind of reaction, also glucina oxide of cerium, tantalic and titanic acids, yttria and zirconia. But if a small portion of silica should be present, then the bead becomes clear. This is likewise the case with some silicates, provided there be not too large a quantity present, that is: over the quantity necessary to saturate the borax, for, in that case, the bead will be opaque when cool.

If the bead be heated on charcoal, a small tube or cavity must be scooped out of the charcoal, the bead placed in it, and the flame of reduction played upon it. When the bead is perfectly fused, it is taken up between the platinum forceps and pressed flat, so that the color may be the more readily discerned. This quick cooling also prevents the protoxides, if there be any present, from passing into a higher degree of oxidation.

The bead should first be submitted to the oxidation flame, and any reaction carefully observed. Then the bead should be submitted to the flame of reduction. It must be observed that the platinum forceps should not be used when there is danger of a metallic oxide being reduced, as in this case the metal would alloy with the platinum and spoil the forceps. In this case charcoal should be used for the support. If, however, there be oxides present which are not reduced by the borax, then the platinum loop may be used. Tin is frequently used for the purpose of enabling the bead to acquire a color for an oxide in the reducing flame, by its affinity for oxygen. The oxide, thus being reduced to a lower degree of oxidation, imparts its peculiar tinge to the bead as it cools.

The arsenides and sulphides, before being examined, should be roasted, and then heated with the borax bead. The arsenic of the former, it should be observed, will act on the glass tube in which the sublimation is proceeding, if the glass should contain lead.

It should be recollected that earths, metallic oxides, and metallic acids are soluble in borax, except those of the easily reducible metals, such as platinum or gold, or of mercury, which too readily vaporize. Also the metallic sulphides, after the sulphur has been driven off. Also the salts of metals, after their acids are driven off by heat. Also the nitrates and carbonates, after their acids are driven off during the fusion. Also the salts of the halogens, such as the chlorides, iodides, bromides, etc., of the metals. Also the silicates, but with great tardiness. Also the phosphates and borates that fuse in the bead without suffering decomposition. The metallic sulphides are insoluble in borax, and many of the metals in the pure state.

There are many substances which give clear beads with borax both while hot and cold, but which, upon being heated with the intermittent oxidation flame, become enamelled and opaque. The intermittent flame may be readily attained, not by varying the force of the air from the mouth, but by raising and depressing the bead before the point of the steady oxidating flame. The addition of a little nitrate of potash will often greatly facilitate the production of a color, as it oxidizes the metal. The hot bead should be pressed upon a small crystal of the nitrate, when the bead swells, intumesces, and the color is manifested in the surface of the bead,

6. EXAMINATIONS IN MICROCOSMIC SALT.

Microcosmic salt is a better flux for many metallic oxides than borax, as the colors are exhibited in it with more strength and character. Microcosmic salt is the phosphate of soda and ammonia. When it is ignited it passes into the biphosphate of soda, the ammonia being driven off. This biphosphate of soda possesses an excess of phosphoric acid, and thus has the property of dissolving a great number of substances, in fact almost any one, with the exception of silica. If the substances treated with this salt consist of sulphides or arsenides, the bead must be heated on charcoal. But if the substance experimented upon consists of earthly ingredients or metallic oxides, the platinum wire is the best. If the latter is used a few additional turns should be given to the wire in consequence of the greater fluidity of the bead over that of borax. The microcosmic salt bead possesses the advantage over that of borax, that the colors of many substances are better discerned in it, and that it separates the acids, the more volatile ones being dissipated, while the fixed ones combine with a portion of the base equally with the phosphoric acid, or else do not combine at all, but float about in the bead, as is the case particularly with silicic acid. Many of the silicates give with borax a clear bead, while they form with microcosmic salt an opalescent one.

It frequently happens, that if a metallic oxide will not give its peculiar color in one of the flames, that it will in the other, as the difference in degree with which the metal is oxidized often determines the color. If the bead is heated in the reducing flame, it is well that it should be cooled rapidly to prevent a reoxidation. Reduction is much facilitated by the employment of metallic tin, whereby the protoxide or the reduced metal may be obtained in a comparatively brief time.

The following tables, taken from Plattner and Sherer, will present the reactions of the metallic oxides, and some of the metallic acids, in such a clear light, that the student cannot very easily be led astray, if he gives the least attention to them. It frequently happens that a tabular statement of reactions will impress facts upon the memory when long detailed descriptions will fail to do so. It is for this purpose that we subjoin the following excellent tables.

* * * * *

TABLE I.

A. BORAX. 1. Oxydizing flame. 2. Reducing "

B. MICROCOSMIC SALT. 1. Oxydizing flame. 2. Reducing "

A. BORAX

1. Oxydizing flame

Color of Bead. + - Substances which produce this color + in the hot bead. in the cold bead. Colorless - Silica Silica Alumina Alumina _ Oxide of Tin Oxide of Tin Telluric Acid Telluric Acid Baryta Baryta Strontia Strontia Lime Lime Magnesia Magnesia Glucina In all Glucina Yttria } proportions. Yttria Zirconia Zirconia Thoria Thoria With Oxide of Lanthanum Oxide of Lanthanum intermittent " " Silver }flame Tantalic Acid Tantalic Acid opaque Niobic " Niobic " white. Pelopic " / Pelopic " Titanic " _/ Titanic " _ Tungstic " In small Tungstic " Molybdic " quantity Molybdic " Oxide of Zinc only. Oxide of Zinc / " " Cadmium } " " Cadmium_/ " " Lead In large " " Lead " " Bismuth / quantity " " Bismuth " " Antimony / yellow. " " Antimony - Yellow, orange-red and reddish-brown. - _ Titanic Acid, yellow Tungstic Acid, yellow Molybdic Acid, dark yellow when in Oxide of Zinc, pale-yellow large Oxide of Cadmium, }quantity. pale-yellow Otherwise Oxide of Lead, yellow colorless. Oxide of Bismuth, orange / Oxide of Antimony, yellow/ Oxide of Cerium, red Oxide of Cerium with interm. Oxide of Iron, dark red flame opaque white. Oxide of Uranium, red Oxide of Iron, yellow Oxide of Silver Oxide of Uranium with interm. flame opaque yellow. Oxide of Silver in large proportion, with interm. flame yellow. Vanadic Acid, yellow Vanadic Acid, yellow. Oxide of Chromium, dark-red Oxide of Nickel, reddish-brown. Oxide of Manganese, red to violet. Violet or Amethyst. Oxide of Nickel " " Manganese Oxide of Didymium. " " Didymium Blue. Oxide of Cobalt Oxide of Cobalt. " Copper, blue to greenish-blue. Green. Oxide of Copper Oxide of Chromium, with yellowish tinge.

A. BORAX

2. Reducing flame

+ + Color of Bead. + - Substances which produce this color + + in the hot bead. in the cold bead. + + Colorless + + Silica Silica Alumina Alumina Oxide of Tin Oxide of Tin Baryta Baryta Strontia Strontia Lime Lime Magnesia Magnesia With Glucina Glucina intermittent Yttria Yttria }flame Zirconia Zirconia opaque-white. Thoria Thoria only when saturated Oxide of Lanthanum Oxide of Lanthanum " " Cerium " " Cerium / Tantalic Acid Tantalic Acid / Oxide of Didymium Oxide of Didymium " " Manganese " " Manganese Niobic Acid In small Niobic Acid In small Pelopic " } proportions. Pelopic " } proportions. / / Oxide of Silver Oxide of Silver After " " Zinc After long " " Zinc long " " Cadmium continued " " Cadmium continued " " Lead } blowing. " " Lead } blowing. " " Bismuth Otherwise " " Bismuth Otherwise " " Antimony grey. " " Antimony grey. " " Nickel / " " Nickel / Telluric Acid / Telluric Acid / + + Yellow to brown. + + Titanic Acid Titanic Acid. Tungstic " Tungstic " Molybdic " Molybdic " Vanadic " + + Blue. + + Oxide of Cobalt. Oxide of Cobalt. Titanic Acid with intermittent flame opaque-blue. + + Green. + + Oxide of Iron Oxide of Iron, bottle-green. " " Uranium Oxide of Uranium, bottle- " " Chromium green. Oxide of Chromium, emerald- green. Vanadic Acid, emerald-green. + + Opaque-grey. (The opacity generally becomes distinct during cooling.) + + Oxide of Silver Oxide of Silver. " " Zinc After " " Zinc After " " Cadmium short " " Cadmium short " " Lead } blowing. " " Lead blowing. " " Bismuth Otherwise " " Bismuth }Otherwise " " Antimony colorless. " " Antimony colorless. " " Nickel / " " Nickel / Telluric Acid / Telluric Acid / Niobic Acid After long Niobic Acid After long Pelopic " continued blowing Pelopic " continued } and in } blowing and considerable in considerable / proportion. / proportion. + + Opaque red and reddish-brown. + + Oxide of Copper Oxide of Copper. + +

B. MICROCOSMIC SALT.

1. Oxydizing flame.

+ + Color of Bead. + - Substances which produce this color + + in the hot bead. in the cold bead. + + Colorless + + _ Silica (only Silica slightly soluble) Alumina Alumina Oxide of Tin Oxide of Tin _ Telluric Acid Telluric Acid Baryta Baryta Strontia Strontia With Lime In all Lime intermittent Magnesia } proportions. Magnesia }flame Glucina Glucina opaque Yttria Yttria white. Zirconia Zirconia Thoria Thoria / Oxide of Lanthanum Oxide of Lanthanum/ " " Cerium Niobic Acid / Niobic Acid Pelopic " _/ Pelopic " Tantalic " Tantalic " Titanic " Titanic " Tungstic " _ Tungstic " Oxide of Zinc In small Oxide of Zinc " " Cadmium quantity only. " " Cadmium " " Lead } In large " " Lead " " Bismuth quantity " " Bismuth " " Antimony / yellow. " " Antimony _/ + + Yellow, orange, red and brown. + + Tantalic Acid _ Titanic " Tungstic " Oxide of Zinc In large " " Cadmium } quantity. " " Lead " " Bismuth " " Antimony _/ " " Silver Oxide of Silver. " " Cerium " " Iron Oxide of Iron. " " Nickel " " Nickel. " " Uranium " " Uranium, yellowish-green. Vanadic Acid Vanadic Acid. Oxide of Chromium + + Violet or Amethyst. + + Oxide of Manganese Oxide of Manganese. " " Didymium " " Didymium. + + Blue. + + Oxide of Cobalt Oxide of Cobalt Oxide of Copper, to greenish-blue. + + Green. + + Molybdic Acid, yellowish-green Molybdic Acid, yellowish-green. Oxide of Copper Oxide of Uranium, yellowish-green. Oxide of Chromium, emerald-green. + +

B. MICROCOSMIC SALT.

2. Reducing flame.

+ + Color of Bead. + - Substances which produce this color + + - in the hot bead. in the cold bead. + + Colorless + + Silica (only slightly soluble) Silica (only slightly soluble). Alumina Alumina. Oxide of Tin Oxide of Tin. _ Baryta Baryta Strontia Strontia Lime Lime Magnesia Magnesia With an Glucina Glucina }intermittent Yttria Yttria flame Zirconia Zirconia opaque- Thoria Thoria only when white. saturated / Oxide of Lanthanum Oxide of Lanthanum/ " " Cerium " " Cerium. " " Didymium " " Didymium. " " Manganese " " Manganese. Tantalic Acid _ Tantalic Acid. Oxide of Silver Oxide of Silver _ " " Zinc " " Zinc After " " Cadmium After long " " Cadmium long " " Lead } continued " " Lead continued " " Bismuth blowing. " " Bismuth } blowing. " " Antimony Otherwise grey. " " Antimony Otherwise " " Nickel / " " Nickel / grey. Telluric Acid _/ Telluric Acid _/ + + Yellow, red, and brown. + + Oxide of Iron, red Oxide of Iron. Titanic Acid, yellow Pelopic Acid, brown Pelopic Acid. Ferruginous Titanic Acid, blood red Ferruginous Titanic Acid. " Niobic " " " Niobic " " Pelopic " " " Pelopic " " Tungstic " " " Tungstic " Vanadic Acid, brownish Oxide of Chromium, reddish + + Violet or Amethyst. + + Niobic Acid in large proportion Niobic Acid in large proportion. Titanic Acid. + + Blue. + + Oxide of Cobalt Oxide of Cobalt. Tungstic Acid Tungstic Acid. Niobic Acid in very large proportion. Niobic Acid in very large proportion. + + Green. + + Oxide of Uranium Oxide of Uranium. Molybdic Acid Molybdic Acid. Vanadic " Oxide of Chromium. + + Opaque-grey. (The opacity generally becomes distinct during cooling.) + + Oxide of Silver Oxide of Silver. " " Zinc " " Zinc. " " Cadmium " " Cadmium. " " Lead " " Lead. " " Bismuth " " Bismuth. " " Antimony " " Antimony. " " Nickel " " Nickel. Telluric Acid Telluric Acid. + + Opaque-red and reddish brown. + + Oxide of Copper Oxide of Copper. + +

* * * * *

TABLE II.

Metallic Oxides

1. Oxide of Cerium, C^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves into a red or dark yellow glass (similar to that produced by iron). During cooling, the color diminishes in the intensity and becomes finally yellow. If much oxide be dissolved, an opaque bead may be obtained with an intermittent flame, and a still larger quantity renders it opaque spontaneously.

in the reducing flame.

The color of the bead becomes paler, so that a bead, which is yellow in the oxidizing flame, is rendered colorless. With a large quantity of oxide the bead becomes white and crystalline on cooling.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax. During the process of cooling the color entirely disappears.

in the reducing flame.

Both, when hot and cold, the bead is colorless, by which character oxide of cerium may be distinguished from oxide of iron. The glass remains clear even when containing a large quantity of the oxide.

* * * * *

2. Oxide of Lanthanum, LaO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves into a colorless glass, which, when sufficient oxide is present, may be rendered opaque with an intermittent flame, and becomes so spontaneously on cooling, when a still larger amount is dissolved.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

No reaction.

* * * * *

3. Oxide of Didymium, DO.

Behavior with Borax on Platinum wire

in the oxidizing flame:

Dissolves to a clear dark amethystine glass.

in the reducing flame.

No reaction.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

No reaction.

* * * * *

4. Oxide of Manganese, Mn^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Affords an intense amethyst color, which on cooling becomes violet. A large quantity of the oxide produces an apparently black bead, which however, if pressed flat, is seen to be transparent.

in the reducing flame.

The colored bead becomes colorless. With a large amount of the oxide, this reaction is best obtained upon charcoal, and is facilitated by the addition of tin foil.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

With a considerable quantity of oxide an amethyst color is obtained, but never so dark as in borax. With but little oxide a colorless bead is obtained, in which, however, the amethyst-color may be brought out by adding a little nitre. While the bead is kept fused, it froths and gives off bubbles of gas.

in the reducing flame.

The colored bead immediately loses its color, either on platinum wire or on charcoal. After the reduction the fluid bead remains still.

* * * * *

5. Oxide of Iron, Fe^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

With a small proportion of oxide, the glass is of a yellow color, while warm, and colorless when cold; with a larger proportion, red, while warm, and yellow, when cold; and with a still larger amount, dark-red, while warm, and dark-yellow, when cold.

in the reducing flame.

Treated alone on platinum wire, the glass becomes of a bottle-green color (F^{3}O^{4}), and if touched with tin, it becomes of a pale sea-green. On charcoal with tin, it assumes at first a bottle-green color, which by continued blowing changes to a sea-green (FeO).

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

With a certain amount of oxide, the glass is of a yellowish-red color, which on cooling changes to yellow, then green, and finally becomes colorless. With a large addition of oxide, the color is, when warm, dark red, and passes, while cooling, into brownish-red, dark green, and finally brownish-red. During the cooling process, the colors change more rapidly than with borax.

in the reducing flame.

With a small proportion of oxide there is no reaction. With a larger amount the bead is red, while warm, and becomes on cooling successively yellow, green, and russet. With the addition of tin the glass becomes, during cooling, first green and then colorless.

* * * * *

6. Oxide of Cobalt, CoO.

Behavior with Borax on Platinum wire

in the oxidizing flame:

Colors the glass of an intense smalt blue both whilst hot and when cold. When much oxide is present, the color is so deep as to appear black.

in the reducing flame:

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax, but less intensively colored. During cooling the color becomes somewhat paler.

in the reducing flame.

As in the oxidizing flames.

* * * * *

7. Oxide of Nickel, NiO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Colors intensely. A small amount of oxide affords a glass which, while warm, is violet, and becomes of a pale reddish-brown on cooling. A larger addition produces a dark violet color in the warm and reddish-brown in the cold bead.

in the reducing flame.

The oxide is reduced and the metallic particles give the bead a turbid grey appearance. If the blast be continued the metallic particles fall together without fusing, and the glass becomes colorless. This reaction is readily obtained with tin upon charcoal, and the reduced nickel fuses to a bead with the tin.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves into a reddish glass which becomes yellow on cooling. With a large addition of the oxide, the glass is brownish while hot, and orange when cold.

in the reducing flame.

On platinum wire the nickeliferous bead undergoes no change. Treated with tin upon charcoal, it becomes at first opaque and grey, and after long continued blowing the reduced nickel forms a bead, and the glass remains colorless.

* * * * *

8. Oxide of Zinc, ZnO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves easily into a clear colorless glass, which, when much oxide is present, may be rendered opaque and flocculent by an intermittent flame, and becomes so spontaneously with a still larger addition. When a considerable quantity is dissolved, a glass is obtained which is pale yellow, while hot, and colorless when cold.

in the reducing flame.

On platinum wire the saturated glass becomes at first opaque and grey, but by a sustained blast is again rendered clear. On charcoal the oxide is gradually reduced; the metal is volatilized and in crusts the charcoal with oxide.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

As with borax.

* * * * *

9. Oxide of Cadmium, CdO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

When in very large proportion, dissolves to a clear yellow glass, which becomes nearly colorless on cooling. When the oxide is present in any considerable quantity, the glass can be rendered opaque with an intermittent flame, and, with a larger addition, it becomes so spontaneously on cooling.

in the reducing flame.

Upon charcoal ebullition takes place and the oxide is reduced. The metallic cadmium is volatilized and incrusts the charcoal with its characteristic deep yellow oxide.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

When in very large proportion dissolves to a clear glass, having a yellow tinge, while hot, which disappears on cooling, and when perfectly saturated, becomes milk-white.

in the reducing flame.

On charcoal the oxide is slowly and imperfectly reduced. The reduced metal forms the characteristic incrustation on the charcoal, but the is thin and does not exhibit its color clearly until quite cold. The addition of tin hastens the reaction.

* * * * *

10. Oxide of Lead, PbO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear yellow glass, which loses its color upon cooling, and when containing much oxide can be rendered dull under an intermittent flame. With a still larger addition of oxide it becomes opaline yellow on cooling.

in the reducing flame.

The plumbiferous glass spreads out on charcoal, becomes turbid, bubbles up, until the whole of the oxide is reduced, when it again becomes clear. It is, however, difficult to bring the lead together into a bead.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax, but a larger addition of oxide, required to produce a yellow color in the warm bead.

in the reducing flame.

On charcoal the plumbiferous glass becomes grey and dull. With an over dose of oxide a part is volatilized and forms an incrustation on the charcoal beyond the bead. The addition of tin does not render the glass opaque, but somewhat more dull and grey than in its absence.

* * * * *

11. Oxide of Tin, SnO^{2}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

In small quantity dissolves slowly into a clear colorless glass, which, when cold, remains clear, and cannot be rendered opaque with an intermittent flame. If a saturated bead, which has been allowed to cool, be reheated to incipient redness, it loses its rounded form and exhibits imperfect crystallization.

in the reducing flame.

A glass containing but little oxide undergoes no change. If much of the latter be present, a part may be reduced upon charcoal.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

In small quantity dissolves very slowly to a colorless glass, which remains clear on cooling.

in the reducing flame.

The glass undergoes no change, either on charcoal or platinum wire.

* * * * *

12. Oxide of Bismuth, BiO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear glass which with a small amount of the oxide is yellow, while warm, and becomes colorless on cooling. With a larger addition, the glass is, in the hot state, of a deep orange color, which changes to yellow and finally becomes opaline in process of cooling.

in the reducing flame.

A glass becomes at first grey and turbid, then begins to effervesce, which action continues during the reduction of the oxide, and it finally becomes perfectly clear. If tin be added, the glass becomes at first grey from the reduced bismuth, but, when the metal is collected into a bead, the glass is again clear and colorless.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves in small quantity to a clear colorless glass. A larger addition affords a glass which, while warm, is yellow, and becomes colorless on cooling. When in sufficient proportion the glass may be rendered opaque under an intermittent flame, and a still larger addition of oxide renders the bead spontaneously opaque on cooling.

in the reducing flame.

On charcoal, and especially with the addition of tin, the glass remains colorless and clear, while warm, but becomes on cooling of a dark grey color and opaque.

* * * * *

13. Oxide of Uranium, U^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Behaves similarly to oxide of iron, with the exception that the color of the former is somewhat paler. When sufficiently saturated, the glass may be rendered of an opaque yellow by an intermittent flame.

in the reducing flame.

Affords the same color as the oxide of iron. The green glass obtained in this flame, if sufficiently saturated, can be rendered black by an intermittent flame, but it has under these circumstances no enameline appearance. On charcoal, with the addition of tin, the glass takes a dark green color.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear yellow glass, which assumes a yellowish-green color on cooling.

in the reducing flame.

The glass assumes a beautiful green color, which becomes more brilliant as the bead cools. The addition of tin upon charcoal produces no further change.

* * * * *

14. Oxide of Copper, CuO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Produces an intense coloration. If in small quantity, the glass is green, while warm, and becomes blue on cooling. If in large proportion, the green color is so intense as to appear black. When cool, this becomes paler, and changes to a greenish blue.

in the reducing flame.

If not too saturated, the cupriferous glass soon becomes nearly colorless, but immediately on solidifying assumes a red color and becomes opaque. By long continued blowing on charcoal, the copper in the bead is reduced and separates out as a small metallic bead, leaving the glass colorless. With the addition of tin, the glass becomes of an opaque dull-red on cooling.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

With an equal proportion of oxide, this salt is not so strongly colored as borax. A small amount imparts a green color in the warm and a blue in the cold. With a very large addition of oxide, the glass is opaque in the hot state, and after cooling of a greenish-blue.

in the reducing flame.

A tolerably saturated glass assumes a dark green color under a good flame, and on cooling becomes of an opaque brick-red, the moment it solidifies. A glass containing but a small proportion of the oxide becomes equally red and opaque on cooling, if treated with tin upon charcoal.

* * * * *

15. Oxide of Mercury, HgO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

* * * * *

16. Oxide of Silver, AgO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

The oxide is partly dissolved and partly reduced. In small quantity, it colors the glass yellow while warm, the color disappearing on cooling. In larger quantity, the glass is yellow while warm, but during cooling becomes paler to a certain point, and then again deeper. If reheated slightly, the glass becomes opalescent.

in the reducing flame.

On charcoal the argentiferous glass becomes at first grey from the reduced metal, but afterwards, when the silver is collected into a bead, it becomes clear and colorless.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Both the oxide and the metal afford a yellowish glass, which, when containing much oxide becomes opaline, exhibiting a yellow color by daylight and a red one by artificial light.

in the reducing flame.

As in borax.

* * * * *

17. Oxide of Platinum, PtO^{2}. 18. Oxide of Palladium, PdO^{2}. 19. Oxide of Rhodium, R^{2}O^{3}. 20. Oxide of Iridium, Ir^{2}O^{3}. 21. Oxide of Ruthenium, Ru^{2}O^{9}. 22. Oxide of Osmium OsO^{2}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Are reduced without being dissolved. The reduced metal, being infusible, cannot however be collected into a bead.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As in borax.

in the reducing flame.

As in borax.

* * * * *

23. Oxide of Gold, Au^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Is reduced without being dissolved and can be collected into a bead on charcoal.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As in borax.

in the reducing flame.

As in borax.

* * * * *

24. Titanic Acid, TiO^{2}

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear glass which, when but little acid is present, is colorless, but when in larger proportion, yellow, and, on cooling, colorless. When sufficiently saturated, it may be rendered opaque with an intermittent flame, and with a still larger addition of the acid becomes so spontaneously on cooling.

in the reducing flame.

In small proportion, it renders the glass yellow in larger quantity dark-yellow or brown. A saturated bead assumes a blue enamel-like appearance under an intermittent flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear glass, which, when sufficiently saturated, is yellow white hot, and becomes colorless on cooling.

in the reducing flame.

The glass obtained in the oxidizing glame becomes yellow in the hot state, but on cooling assumes a beautiful violet color. If too saturated, this color is so deep as to appear opaque, but is not enameline. If the titanic acid contains iron, the glass becomes on cooling of a brownish-yellow or red color. The addition of tin neutralizes the iron, and the glass then becomes violet.

* * * * *

25. Tantalic Acid, TaO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear colorless glass, which, when sufficiently saturated, may be rendered opaque with an intermittent flame, and with a larger addition of the acid becomes spontaneously enameline on cooling.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear glass, which, when it contains a large proportion of the acid, is yellow while warm, but becomes colorless on cooling.

in the reducing flame.

The glass obtained in the oxidizing flame undergoes no change, nor does it, according to H. Rose, alter by the addition of sulphate of iron.

* * * * *

26. Niobic Acid, Ni^{2}O{3}

Behavior with Borax on Platinum wire

in the oxidizing flame.

Behaves in a similar manner to tantalic acid, but the glass requires a very large dose of the acid to render it opaque under an intermittent flame. With an increased amount of the acid, the glass is clear and yellow, while warm, but becomes on cooling turbid, and when quite cold is white.

in the reducing flame.

The glass obtained in the oxidizing flame and which has become opalescent on cooling, is rendered clear in the reducing flame. With a larger addition of the acid, it becomes dull, and of a bluish-grey color on cooling, and a still larger amount of renders it opaque and bluish grey.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves in large quantities to a clear colorless glass.

in the reducing flame.

If the acid be not present in too large a proportion, the glass remains unchanged. An additional amount of the acid renders it violet, and a still larger quantity affords a beautiful pure blue color, similar to that produced by tungstic acid. If to such a bead some sulphate of iron be added, the glass becomes blood-red. The addition of peroxide of iron renders the glass deep yellow while warm, the color becomes paler on cooling.

* * * * *

27. Pelopic Acid, Pp^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Behaves similarly to the preceding.

in the reducing flame.

A bead containing sufficient of the acid to render it spontaneously opaque on cooling, has a greyish color.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves even in large quantity to a colorless glass.

in the reducing flame.

With sufficient dose of the acid, the bead becomes brown with a violet tinge. This reaction is readily obtained upon charcoal. Sulphate of iron renders the bead blood-red.

* * * * *

28. Oxide of Antimony, SbO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Even when in large proportion, dissolves to a clear glass, which is yellow when warm, but almost entirely loses its color on cooling. On charcoal, the antimonious acid may be almost expelled, so that tin produces no further change.

in the reducing flame.

A bead, that has only been treated for a short time in the oxidizing flame, when submitted to the reducing flame becomes grey and turbid from the reduced antimony. This soon volatizes and the glass again becomes clear. The addition of tin renders the glass ash-grey or black, according to the amount of oxide it contains.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves with ebullition to a glass of a pale yellow color while warm.

in the reducing flame.

On charcoal, the saturated glass becomes at first dull, but as soon as the reduced antimony is volatilized, it again becomes clear. With tin, the glass is at first rendered grey by the reduced antimony, but by continued blowing is restored to clearness. Even when the glass contains but little oxide, tin produces this reaction.

* * * * *

29. Tungstic Acid, WO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily to a clear colorless glass. In large proportion it renders the borax yellow, while warm, and with a still greater addition the bead may be made opaque with an intermittent flame. If more be then added, this reaction takes place spontaneously.

in the reducing flame.

When the oxide is present in small quantity, the glass undergoes no change. With a larger proportion, the glass is deep yellow while warm, and yellowish-brown when cold. This reaction takes place upon charcoal, with a small quantity of the acid. Tin produces a dark coloration, when the acid is not present in too great a quantity.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear glass, which, when saturated, is yellow in the hot state.

in the reducing flame.

The glass is of a pure blue. If the tungstic acid contain iron, the glass becomes blood-red on cooling, similar to titanic acid. In this case, tin restores the blue color, or, if iron be in considerable quantity, renders it green.

* * * * *

30. Molydbic Acid, MO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves readily and in large quantity. When but little is dissolved, the glass is yellow while hot and colorless when cold. When in larger quantity yellow while warm and opaline when cold, and a further addition of acid renders it yellow when warm, the color, on cooling, changing first to a pale enamel blue, and then to an enamel white.

in the reducing flame.

The glass, which has been treated in the oxidizing flame, becomes, when the acid is not present in too large a quantity, brown, and when in large quantity, perfectly opaque. In a strong flame, oxide of molybdenum is formed which is visible in the yellow glass in the form of black flakes. If the glass appear opaque, it should be flattened with the forceps.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear glass, which, when sufficient acid is present, is of a yellowish-green color when warm, and becomes nearly colorless on cooling. On charcoal, the glass becomes dark, and when cool has a beautiful green color.

in the reducing flame.

The glass becomes of a bottle-green color, which on cooling, changes to a brilliant green, similar to that produced by oxide of chromium. The reaction on charcoal is precisely similar. Tin renders the color somewhat darker.

* * * * *

31. Vanadic Acid, VaO^{8}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves to a clear glass, which is colorless when only a small quantity of acid is present, and yellow when containing a larger proportion.

in the reducing flame.

The yellow color of the glass changes to a brown when warm and a chrome-green on cooling.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

As with borax.

* * * * *

32. Oxide of Chromium, Cr^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Affords an intense color, but dissolves slowly. A small proportion colors the glass yellow when warm, and yellowish green when cold; a larger addition produces a dark red color when warm, which, on cooling, becomes yellow and finally a brilliant green with a tinge of yellow.

in the reducing flame.

A small quantity of the oxide renders the glass beautifully green both when warm and when cold. A larger addition changes it to a darker emerald green. Tin produces no change in the color.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

Dissolves to a clear glass which has a pink tinge while warm, but on cooling becomes dusky green, and finally brilliantly green.

in the reducing flame.

As in the oxidizing flame, except that the colors are somewhat darker. Tin produces no further change.

* * * * *

33. Arsenious Acid, AsO^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

No reaction.

in the reducing flame.

No reaction.

* * * * *

34. Tellurous Acid, TeO^{2}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Dissolves to a clear colorless glass which, when treated on charcoal, becomes grey and dull from particles of reduced tellurium.

in the reducing flame.

As in the oxidizing flame.

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

As with borax.

in the reducing flame.

As with borax.

* * * * *

7. EXAMINATIONS WITH CARBONATE OF SODA.

The carbonate of soda is pulverized and then kneaded to a paste with water; the substance to be examined, in fine powder, is also mixed with it. A small portion of this paste is placed on the charcoal, and gradually heated until the moisture is expelled, when the heat is brought to the fusion of the bead, or as high as it can be raised. Several phenomena will take place, which must be closely observed. Notice whether the substance fuses with the bead, and if so, whether there is intumescence or not. Or, whether the substance undergoes reduction; or, whether neither of these reactions takes place, and, on the contrary, the soda sinks into the charcoal, leaving the substance intact upon its surface. If intumescence takes place, the presence of either tartaric acid, molybdic acid, silicic, or tungstic acid, is indicated. The silicic acid will fuse into a bead, which becomes clear when it is cold. Titanic acid will fuse into the bead, but may be easily distinguished from the silicic acid by the bead remaining opaque when cold.

Strontia and baryta will flow into the charcoal, but lime will not. The molybdic and tungstic acids combine with the soda, forming the respective salts. These salts are absorbed by the charcoal. If too great a quantity of soda is used, the bead will be quite likely to become opaque upon cooling, while, if too small a quantity of soda is used, a portion of the substance will remain undissolved. These can be equally avoided by either the addition of soda, or the substance experimented upon, as may be required.

As silica and titanic acid are the only two substances that produce a clear bead, the student, if he gets a clear bead, may almost conclude that he is experimenting with silica, titanic acid being a rare substance. When soda is heated with silica, a slight effervescence will be the first phenomenon noticed. This is the escape of the carbonic acid of the carbonate of soda, while the silicic acid takes its place, forming a glass with the soda. As titanic acid will not act in the same manner as silica, it can be easily distinguished by its bead not being perfectly pellucid. If the bead with which silica is fused should be tinted of a hyacinth or yellow color, this may be attributed to the presence of a small quantity of sulphur or a sulphate, and this sometimes happens from the fact of the flux containing sulphate of soda. The following metals, when exposed with carbonate of soda to the reducing flame, are wholly or partially reduced, viz. the oxides of all the noble metals, the oxides and acids of tungsten, molybdenum, arsenic, antimony, mercury, copper, tellurium, zinc, lead, bismuth, tin, cadmium, iron, nickel, and cobalt. Mercury and arsenic, as soon as they are reduced, are dissipated, while tellurium, bismuth, lead, antimony, cadmium, and zinc, are only partially volatilized, and, therefore, form sublimates on the charcoal. Those metals which are difficult of reduction should be fused with oxalate of potassa, instead of the carbonate of soda. The carbonic oxide formed from the combustion of the acid of this salt is very efficient in the reduction of these metals. Carbonate of soda is very efficient for the detection of minute quantities of manganese. The mixture of the carbonate of soda with a small addition of nitrate of potassa, and the mineral containing manganese, must be fused on platinum foil. The fused mass, when cooled, presents a fine blue color.

* * * * *

1. The following minerals, according to Griffin, produce beads with soda, but do not fuse when heated alone: quartz, agalmatolyte, dioptase, hisingerite, sideroschilosite, leucite, rutile, pyrophyllite, wolckonskoite.

2. The following minerals produce only slags with soda: allophane, cymophane, polymignite, aeschynite, oerstedtite, titaniferous iron, tantalite, oxides of iron, yttro-tantalite, oxides of manganese, peroxide of tin (is reduced), hydrate of alumina, hydrate of magnesia, spinel, gahnite, worthite, carbonate of zinc, pechuran, zircon, thorite, andalusite, staurolite, gehlenite, chlorite spar, chrome ochre, uwarowite, chromate of iron, carbonates of the earths, carbonates of the metallic oxides, basic phosphate of yttria, do. of alumina, do. of lime, persulphate of iron, sulphate of alumina, aluminite, alumstone, fluoride of cerium, yttrocerite, topaz, corundum, pleonaste, chondrodite.

3. The following minerals produce beads with a small quantity of soda, but produce slags if too much soda is added: phenakite, pierosmine, olivine, cerite, cyanite, talc, gadolinite, lithium-tourmaline.

* * * * *

1. The following minerals, when fused alone, produce beads. Of these minerals the following produce beads with soda: the zeolites, spodumene, soda-spodumene, labrador, scapolite, sodalite (Greenland), elaeolite, mica from primitive lime-stone, black talc, acmite, krokidolite, lievrite, cronstedtite, garnet, cerine, helvine, gadolinite, boracic acid, hydroboracite, tincal, boracite, datholite, botryolite, axinite, lapis lazuli, eudialyte, pyrosmalite, cryolite.

2. The following minerals produce beads with a small quantity of soda, but if too much is added they produce slags: okenite, pectolite, red silicate of manganese, black hydro-silicate of manganese, idocrase, manganesian garnets, orthite, pyrorthite, sordawalite, sodalite, fluorspar.

3. The following minerals produce a slag with soda: brevicite, amphodelite, chlorite, fahlunite, pyrope, soap-stone (Cornish) red dichroite, pyrargillite, black potash tourmaline, wolfram, pharmacolite, scorodite, arseniate of iron, tetraphyline, hetepozite, uranite, phosphate of iron, do. of strontia, do. of magnesia, polyhalite, hauyne.

4. The following metals are reduced by soda: tungstate of lead, molybdate of lead, vanadate of lead, chromate of lead, vauquelinite, cobalt bloom, nickel ochre, phosphate of copper, sulphate of lead, chloride of lead, and chloride of silver.

* * * * *

The following minerals fuse on the edges alone, when heated in the blowpipe flame:

1. The following produce beads with soda: steatite, meerschaum, felspar, albite, petalite, nepheline, anorthite, emerald, euclase, turquois, sodalite (Vesuvius).

2. The following minerals produce beads with a small quantity of soda, but with the addition of more produce slags: tabular spar, diallage, hypersthene, epidote, zoisite.

3. The following minerals produce slags only with soda: stilpnosiderite, plombgomme, serpentine, silicate of manganese (from Piedmont), mica from granite, pimelite, pinite, blue dichroite, sphenc, karpholite, pyrochlore, tungstate of lime, green soda tourmaline, lazulite, heavy spar, gypsum.

* * * * *

The reactions of substances, when fused with soda in the flame of oxidation may be of use to the student. A few of them are therefore given. Silica gives a clear glass.

The oxide of tellurium and telluric acid gives a clear bead when it is hot, but white after it is cooled.

Titanic acid gives a yellow bead when hot.

The oxide of chromium gives also a clear yellow glass when hot, but is opaque when cold.

Molybdic acid gives a clear bead when hot, but is turbid and white after cooling.

The oxides and acids of antimony give a clear and colorless bead while hot, and white after cooling.

Vanadic acid is absorbed by the charcoal, although it is not reduced.

Tungstic acid gives a dark yellow clear bead while hot, but is opaque and yellow when cold.

The oxides of manganese give to the soda bead a fine characteristic green color. This is the case with a very small quantity. This reaction is best exhibited on platinum foil.

Oxide of cobalt gives to the bead while hot a red color, which, upon being cooled, becomes grey.

The oxide of copper gives a clear green bead while hot.

The oxide of lead gives a clear colorless bead while hot, which becomes, upon cooling, of a dirty yellow color and opaque.

* * * * *

The following metals, when they are fused with soda on charcoal, in the flame of reduction, produce volatile oxides, and leave an incrustation around the assay, viz. bismuth, zinc, lead, cadmium, antimony, selenium, tellurium, and arsenic.

Bismuth, under the reduction flame, yields small particles of metal, which are brittle and easily crushed. The incrustation is of a flesh color, or orange, when hot, but gets lighter as it cools. The sublimate may be driven about the charcoal from place to place, by either flame, but is finally dissipated. While antimony and tellurium, in the act of dissipation, give color to the flame, bismuth does not, and may thus be distinguished from them.

Zinc deposits an incrustation about the assay, which is yellow while hot, but fades to white when cold. The reduction flame dissipates this deposit, but not that of oxidation. All the zinc minerals deposit the oxide incrustation about the assay, which, when moistened with a solution of cobalt and heated, changes to green.

Lead is very easily reduced, in small particles, and may be easily distinguished by its flattening under the hammer, unlike bismuth. It leaves an incrustation around the assay resembling that of bismuth, in the color of it, and in the peculiar manner in which it lies around the assay.

Cadmium deposits a dull reddish incrustation around the assay. Either of the flames dissipate the sublimate with the greatest readiness.

Antimony reduces with readiness. At the same time it yields considerable vapor, and deposits an incrustation around the assay. This deposit can be driven about on the charcoal by either of the flames. The flame of reduction, however, produces the light blue color of the antimony.

Selenium is deposited on the charcoal as a grey metallic-looking sublimate, but sometimes appearing purple or blue. If the reduction flame is directed on this deposit, it is dissipated with a blue light.

Tellurium is deposited on the charcoal as a white sublimate, sometimes changing at the margin to an orange or red color. The oxidation flame drives the deposit over the charcoal, while the reduction-flame dissipates it with a greenish color.

Arsenic is vaporized rapidly, while there is deposited around the assay a white incrustation of arsenious acid. This deposit will extend to some distance from the assay, and is readily volatilized, the reducing flame producing the characteristic alliaceous color.

* * * * *

The following metals, or their compounds, are reduced when fused with soda on charcoal, in the flame of reduction. They are reduced to metallic particles, but give no incrustation, viz. nickel, cobalt, iron, tin, copper, gold, silver, platinum, tungsten, and molybdenum.

The particles of iron, nickel, and cobalt, it should be borne in mind, are attracted by the magnet.

The following substances are neither fused nor reduced in soda, viz. alumina, magnesia, lime, baryta, strontia, the oxide of uranium, the oxides of cerium, zirconia, tantalic acid, thorina, glucina, and yttria. Neither are the alkalies, as they sink into the charcoal. The carbonates of the earths, strontia, and baryta fuse.

* * * * *



Part III

SPECIAL REACTIONS; OR, THE BEHAVIOR OF SUBSTANCES BEFORE THE BLOWPIPE.

Analytical chemistry may be termed the art of converting the unknown constituents of substances, by means of certain operations, into new combinations which we recognize through the physical and chemical properties which they manifest.

It is, therefore, indispensably necessary, not only to be cognizant of the peculiar conditions by which these operations can be effected, but it is absolutely necessary to be acquainted with the forms and combinations of the resulting product, and with every modification which may be produced by altering the conditions of the analysis.

We shall first give the behavior of simple substances before the blowpipe; and the student should study this part thoroughly, by repeating each reaction, so that he can acquire a knowledge of the color, form, and physical properties in general, of the resulting combination. There is nothing, perhaps, which will contribute more readily to the progress of the pupil, than thorough practice with the reactions recommended in this part of the work, for when once the student shall have acquired a practical eye in the discernment of the peculiar appearances of substances after they have undergone the decompositions produced by the strong heat of the blowpipe flame, together with the reactions incident to these changes, then he will have greatly progressed in his study, and the rest will be comparatively simple.

A. METALLIC OXIDES.

GROUP FIRST.—THE ALKALIES: POTASSA, SODA, AMMONIA, AND LITHIA.

The alkalies, in their pure, or carbonated state, render reddened litmus paper blue. This is likewise the case with the sulphides of the alkalies. The neutral salts of the alkalies, formed with the strong acids, do not change litmus paper, but the salts formed with the weak acids, render the red litmus paper blue; for instance, the alkaline salts with boracic acid. Fused with borax, soda, or microcosmic salt, they give a clear bead. The alkalies and their salts melt at a low red heat. The alkalies cannot be reduced to the metallic state before the blowpipe. They are not volatile when red hot, except the alkali ammonia, but they are volatile at a white heat.

(a.) Potassa.(KO).—It is not found free, but in combination with inorganic and organic acids, as well in the animal as in the vegetable organism, as in the mineral kingdom. In the pure, or anhydrous state, or as the carbonate, potassa absorbs moisture, and becomes fluid, or is deliquescent, as it is termed. By exposing potassa, or its easily fusible salts (except the phosphate or borate), upon platinum wire, to the point of the blue flame, there is communicated to the external flame a violet color, in consequence of a reduction and reoxidation. This color, though characteristic of all the potassa compounds, is scarcely visible with the phosphate or borate salts of that alkali. The admixture of a very little soda (1/300th) destroys the color imparted by the potassa, while the flame assumes a yellow color, characteristic of the soda. The presence of lithia changes the violet color of the potash into red. The silicates of potassa must exist in pretty large proportion before they can be detected by the violet color of the flame, and those minerals must melt easily at the edges. The presence of a little soda in these instances conceals the reaction in the potassa entirely.

If alcohol is poured over potassa compounds which are powdered, and then set on fire, the external flame appears violet-colored, particularly when stirred with a glass rod, and when the alcohol is really consumed. The presence of soda in lithia will, in this case likewise, hide by their own characteristic color, that of the potassa.

The salts of potassa are absorbed when fused upon charcoal. The sulphur, bromine, chlorine, and iodine compounds of potassa give a white, but easily volatile sublimate upon the charcoal, around the place where the fused substance reposed. This white sublimate manifests itself only when the substance is melted and absorbed within the charcoal, and ceases to be visible as soon as it is submitted to the reducing flame, while the external flame is colored violet; sulphate of potassa, for instance, is reduced by the glowing charcoal into the sulphide. This latter is somewhat volatile, but by passing through the oxidation flame, it is again oxidized into the sulphate. This, being less volatile, sublimes upon the charcoal, but by exposing it again to the flame of reduction, it is reduced and carried off to be again oxidized by its passage through the oxidation flame.

Potassa and its compounds give, with soda, borax or microcosmic salt, as well when hot as cold, colorless beads, unless the acid associated with the alkali should itself produce a color. When borax is fused with some pure boracic acid, and sufficient of the oxide of nickel is added, so that the beads appear of a brown color after being cooled, and then the bead thus produced fused with the substance suspected to contain potassa, in the oxidation flame, the brown color is changed to blue. The presence of the other alkalies does not prevent this reaction. As it is not possible to detect potassa compounds with unerring certainty by the blowpipe flame, the the wet method should be resorted to for the purpose of confirming it.

The silicates of potassa must be prepared as follows, for analytical purposes by the wet way. Mix one part of the finely powdered substance with two parts of soda (free from potassa), and one part of borax. Fuse the mixture upon charcoal in the oxidation flame to a clear, transparent bead. This is to be exposed again with the pincers to the oxidation flame, to burn off the adhering coal particles. Then pulverize and dissolve in hydrochloric acid to separate the silica; evaporate to dryness, dissolve the residue in water, with the admixture of a little alcohol, and test the filtrate with chloride of platinum for potassa.

(b.) Soda (NaO).—This is one of the most abundant substances, although seldom found free, but combined with chlorine or some other less abundant compound. Soda, its hydrate and salts manifest in general the same properties as their respective potash compounds; but the salts of soda mostly contain crystal water, which leaves the salts if they are exposed to the air, and the salts effervesce.

By exposing soda or its compounds upon a platinum wire to the blue flame, a reddish-yellow color is communicated to the external flame, which appears as a long brilliant stream and considerably increased in volume. The presence of potash does not prevent this reaction of soda. If there is too large a quantity of potash, the flame near to the substance is violet-colored, but the edge of the flame exhibits the characteristic tint of the soda. The presence of lithia changes the yellow color to a shade of red.