Chapter VIII: Part III (3)

(_a._) _Copper_ (Cu).--This metal occurs in the metallic state, also as the protoxide, and as oxides combined with acids in different salts (carbonate of copper as malachite, etc.) The sulphide of copper is the principal ore of copper occurring in nature. In the metallic state, copper is of a red color, has great lustre and tenacity, is ductile and malleable, and crystallizes in octahedrons and cubes. It melts at a bright red heat, is more difficult than silver to fuse, but fuses more readily than gold. It absorbs oxygen while melting. There arises from its surface a fine dust of metallic globules, which are covered with the protoxide. The surface of the metal is likewise covered with the protoxide. Copper exposed to moist air tarnishes, and is converted into hydratic carbonate of copper. When ignited in the open air, it is soon covered with the brownish-red protoxide.

([chi].) _Protoxide of Copper_ (Cu^{2}O).--This oxide occurs in nature, crystallized in octahedrons of a ruby-red color, of a lamellar structure, and transparent. Artificially prepared, it forms a powder of the same color. It is decomposed by dilute acids into salts of peroxide and metal. It is converted by ignition, with free access of air, into peroxide.

([beta].) _Oxide of Copper_ (CuO).--This oxide is a dark-brown or black powder. It is dissolved by acids, with a blue or green-colored solution. It is soluble in aqua ammonia, and the solution is of a dark blue color.

_Reactions before the Blowpipe._--Oxide of copper exposed upon platinum wire to the inmost flame (the blue flame), communicates to the external flame a green color. Heated upon charcoal in the oxidation flame, it melts to a black ball, soon spreads over the charcoal, and is partially reduced.

Exposed to the reduction flame, at a temperature which will not melt copper, it is reduced with a bright metallic lustre, but as soon as the blast ceases, the surface of the metal becomes oxidized, and appears dark brown or black. If the temperature is continued still higher, it melts to a metallic grain.

_Borax_ dissolves the oxide of copper in the flame of oxidation to a clear green-colored bead, even if the quantity of oxide be quite small, but by cooling, the bead becomes blue. In the flame of reduction upon platinum wire, the bead soon becomes colorless, but while cooling presents a red color (protoxide of copper). This bead is opaque, but, if too much of the oxide is added, a part of it is reduced to metal, which is visible by breaking the metallic grain.

Upon charcoal, the oxide is reduced to the metal, and the bead appears colorless after cooling. With the addition of some tin, the bead becomes brownish-red and opaque after cooling.

_Microcosmic Salt_ dissolves oxide of copper in the flame of oxidation to a green bead, not so intensely colored as the borax bead. In the reduction flame the bead, if pretty well saturated, becomes dark-green while hot, and brownish-red when cool, opaque and enamel-like. If the oxide is so little that no reaction is visible, by the addition of some tin, the bead appears colorless while hot, and dark brownish-red and opaque when cold.

_Carbonate of Soda_ dissolves oxide of copper in the oxidation flame upon platinum wire, to a clear, green bead, which loses its color when cooling, and becomes opaque.

Upon charcoal, it is reduced to the metal, the soda is absorbed by the charcoal, and the metallic particles melt with sufficient heat to a grain.

(_b._) _Silver_ (Ag).--This metal occurs in nature in the metallic state, and in combination with other metals, particularly with lead. It also occurs as the sulphide in several mines. It crystallizes in cubes and octahedrons; is of a pure white color, great lustre, is very malleable and ductile, and is softer than copper, but harder than gold. It is not oxidizable, neither at common temperatures nor at those which are considerably higher. It is soluble in dilute nitric acid, and in boiling concentrated sulphuric acid.

([chi].) _Protoxide of Silver_ (Ag^{2}O).--It is a black powder. It is converted by acids and ammonia into oxide and metal.

([beta].) _Oxide of Silver_ (AgO).--It is a greyish-brown or black powder, and is the base of the silver salts. With aqua ammonia, it is converted into the black, fulminating silver.

([gamma].) _Superoxide or Binoxide of Silver_ (AgO^{2}).--This oxide occurs in black needles or octahedral crystals of great metallic lustre. It is dissolved by the oxygen acids with the disengagement of oxygen gas.

_Behavior before the Blowpipe._--When exposed to the flames of oxidation and reduction, the oxides of silver are instantly reduced to the metallic state.

_Borax_ dissolves silver-oxides upon platinum wire in the oxidation flame but partially, while the other portion is reduced, the bead appearing opalescent after cooling, in correspondence to the degree of saturation. The bead becomes grey in the flame of reduction, the reduced silver melting to a grain, and the bead is rendered clear and colorless again.

_Microcosmic Salt_ dissolves oxides of silver in the flame of oxidation upon platinum wire to a transparent yellowish bead, which presents, when much of the oxide is present, an opalescent appearance.

In the flame of reduction, the reaction is analogous to that of borax.

By fusion with carbonate of soda in the oxidation and reduction flames, the silver oxides are instantly reduced to metallic silver, which fuses into one or more grains.

(_c._) _Gold_ (Au).--This metal occurs mostly in the metallic state, but frequently mixed with ores, and with other metals. Gold crystallizes in cubes and octahedrons, is of a beautiful yellow color, great lustre, and is the most malleable and ductile of all the metals. It melts at a higher temperature than copper, gives a green colored light when fused, and contracts greatly when cooling. It does not oxidize at ordinary temperatures, nor when heated much above them. It is soluble in nitro-hydrochloric acid (_aqua regia_).

([chi].) _Protoxide of Gold_ (Au^{2}O).--This oxide is a dark violet colored powder which is converted by a temperature of 540 deg. into metallic gold and oxygen. It is only soluble in aqua regia. Treated with hydrochloric acid, it yields the chloride of gold and the metal. With aqua ammonia, it yields the fulminating gold, which is a blue mass and very explosive.

([chi].) _Peroxide of Gold_ (Au^{2}O^{3}).--This oxide is an olive-green or dark brown powder, containing variable quantities of water. Decomposed at 530 deg., it yields metallic gold and oxygen.

_Reactions before the Blowpipe._--Oxides of gold are reduced, in both the oxidation and reduction flames, to the metal, which fuses to grains.

_Borax_ does not dissolve it, but it is reduced to the metallic state in this flux in either flame. The reduced metal fuses upon charcoal to a grain.

_Microcosmic Salt_ presents the same reactions as borax.

When fused with soda, upon charcoal, the soda is absorbed, and the gold remains as a metallic grain.

TENTH GROUP.--MOLYBDENUM, OSMIUM.

These metals are not volatile, and are infusible before the blowpipe; but some of their oxides are volatile, and can be reduced to an infusible metallic powder.

(_a._) _Molybdenum_ (Mo) occurs in the metallic state; also combined with sulphur, or as molybdic acid combined with lead. It is a white, brittle metal, and is unaltered by exposure to the air. When heated until it begins to glow, it is converted into a brown oxide. Heated at a continued dull red heat, it turns blue. At a higher temperature, it is oxidized to molybdic acid, when it glimmers and smokes, and is converted into crystallized molybdic acid upon the surface.

([chi].) _Protoxide of Molybdenum_ (MoO).--This oxide is a black powder.

([chi].) _Deutoxide of Molybdenum_ (MoO^{2}).--This oxide is a dark copper-colored crystalline powder.

_Reactions before the Blowpipe._--Metallic molybdenum, its protoxide and binoxide, are converted in the oxidation flame into molybdic acid. This acid fuses in the flame of oxidation to a brown liquid, which spreads, volatilizes, and sublimes upon the charcoal as a yellow powder, which appears crystalline in the vicinity of the assay. This sublimate becomes white after cooling. Beyond this sublimate there is visible a thin and not volatile ore of binoxide, after cooling; this is of a dark copper-red color, and presenting a metallic lustre.

Heated in a glass tube, closed at one end, it melts to a brown mass, vaporizes and sublimates to a white powder upon a cool portion of the tube. Immediately above the assay, yellow crystals are visible; these crystals are colorless after cooling, and the fused mass becomes light yellow-colored and crystalline.

Upon platinum foil, in the flame of oxidation, it melts and vaporizes, and becomes light yellow and crystalline after cooling. In the reduction flame it becomes blue, and brown-colored if the heat is increased.

Upon charcoal, in the reduction flame, it is absorbed by the charcoal; and, with an increase of the temperature, it is reduced to the metal, which remains as a grey powder after washing off the particles of charcoal.

_Borax_ dissolves it, in the oxidation flame, upon platinum wire easily, and in great quantity, to a clear yellow, which becomes colorless while cooling. By the addition of more of the molybdenic acid the bead is dark yellow, or red while hot, and opalescent when cold. In the reduction flame, the color of the bead is changed to brown and transparent. By the addition of more of the acid, it becomes opaque.

_Microcosmic Salt_ dissolves it in the oxidation flame, upon platinum wire, to a clear, yellowish-green bead, which becomes colorless after cooling. In the reduction flame the bead is very dark and opaque, but becomes of a bright green after cooling. This is the case likewise upon charcoal.

_Carbonate of Soda_ dissolves it upon platinum wire in the oxidation flame with intumescence, to a clear bead, which appears milk-white after cooling. Upon charcoal the soda and the molybdic acid are absorbed, the latter is reduced to the metallic state, the metal remaining as a grey powder after washing off the particles of charcoal. When molybdic acid, or any other oxide of this metal, is exposed upon platinum wire, or with platinum tongs, to the point of the blue flame, a yellowish-green color is communicated to the external flame. If also any of the compounds of molybdenum are mixed in the form of a powder with concentrated sulphuric acid and alcohol, and the latter inflamed, the flame of the alcohol appears colored green.

(_c._) _Osmium_ (Os).--This metal occurs associated with platinum. It is of a bluish-grey color, and is very brittle. Ignited in the open air, it is oxidized to volatile osmic acid, which is possessed of a pungent smell, and affects the eyes. It communicates a bright white color to the flame of alcohol. Osmium oxide (OsO^{2}) is converted in the oxidation flame to osmic acid, which is volatilized with a peculiar smell, leaving a sublimate.

In the reduction flame it is reduced to a dark-brown infusible metallic powder. It produces no reactions with fluxes. Carbonate of soda reduces it upon charcoal to an infusible metallic powder, which appears, after washing off the particles of charcoal, of a dark-brown color.

ELEVENTH GROUP.--PLATINUM, PALLADIUM, IRIDIUM, RHODIUM, RUTHENIUM.

These metals are infusible before the blowpipe. They are not volatile, nor are they oxidizable. Their oxides are, in both flames, reduced to a metallic and infusible powder. They give no reactions with fluxes, but are separated in the metallic form. These metals are generally found associated together in the native platinum, also with traces of copper, lead, and iron.

The metal palladium is found native, associated with iridium and platinum. This metal generally occurs in greatest quantity in Brazil.

The metal rhodium is found along with platinum, but in very small quantities.

Iridium occurs in nature associated with osmium, gold, and platinum, in the mines of Russia. Its great hardness has rendered it desirable for the points of gold pens. In South America this metal is found native, associated with platinum and osmium. The latter metal, associated with platinum and iridium, has been found in South America.

As these metals will not oxidize or dissolve, they cannot be separated from each other by the blowpipe with the reagents peculiar to that species of analysis. It is true that colors may be discerned in the beads, but these tints proceed from the presence of small traces of copper, iron, etc.

The ore of osmium and iridium can be decomposed, and the former recognized by its fetid odor. This metal, strongly ignited in a glass tube with nitrate of potash, is converted to the oxide of osmium, which gives an odor not unlike the chloride of sulphur.

As the metals of this group are very rare ones, especially the last four ones, we shall not devote an especial division to each of them. For a more detailed statement of their reactions, the student is referred to the large works upon blowpipe analysis.

CLASS III.

NON-METALLIC SUBSTANCES.

1. _Water_--2. _Nitric Acid_--3. _Carbon_--4. _Phosphorus_ --5. _Sulphur_--6. _Boron_--7. _Silicon_--8. _Chlorine_ --9. _Bromine_--10. _Iodine_--11. _Fluorine_--12. _Cyanogen_ --13. _Selenium_.

(1.) _Water_ (HO).--Pure distilled water is composed of one volume of oxygen, and two volumes of hydrogen gases; or, by weight, of one part of hydrogen to eight parts of oxygen gases. Water is never found pure in nature, but possessing great solvent properties, it always is found with variable proportions of those substances it is most liable to meet with, dissolved in it. Thus it derives various designations depending upon the nature of the substance it may hold in solution, as lime-water, etc.

In taking cognizance of water in relation to blowpipe analysis, we regard it only as existing in minerals. The examination for water is generally performed thus: the substance may be placed in a dry tube, and then submitted to heat over a spirit-lamp. If the water exists in the mineral mechanically it will soon be driven off, but if it exists chemically combined, the heat will fail to drive it off, or if it does, it will only partially effect it. The water will condense upon the cool portions of the tube, where it can be readily discerned. If the water exists chemically combined, a much stronger heat must be applied in order to separate it.

Many substances may be perhaps mistaken for water by the beginner, such as the volatile acids, etc.

(2.) _Nitric Acid_ (NO^{5}).--Nitric acid occurs in nature in potash and soda saltpetre. These salts are generally impure, containing lime, as the sulphate, carbonate and nitrate, and also iron in small quantity. The soda saltpetre generally contains a quantity of the chloride of sodium. The salts containing nitric acid deflagrate when heated on charcoal. Substances containing nitric acid may be heated in a glass tube closed at one end, by which the characteristic red fumes of nitrous acid are eliminated. If the acid be in too minute a quantity to be thus distinguished, a portion of the substance may be intimately mixed with some bisulphate of potash, and treated as above. The sulphuric acid of the bisulphate combines with the base, and liberates the nitric acid, while the tube contains the nitrous acid gas.

The nitrate of potassa, when heated in a glass tube, fuses to a clear glass, but gives off no water. When fused on platinum wire, it communicates to the external flame the characteristic violet color. When fused and ignited on charcoal, its surface becomes frothy, indicating the nitric acid.

(3.) _Carbon_ (C).--Carbon is found in nature in the pure crystallized state as the diamond. It occurs likewise in several allotropic states as graphite, plumbago, charcoal, anthracite, etc. It exists in large quantities combined with oxygen as carbonic acid.

The diamond, although combustible, requires too high a heat for its combustion to enable us to burn it with the blowpipe. When excluded from the air, it may be heated to whiteness without undergoing fusion, but with the free access of air it burns at a temperature of 703 deg. C, and is converted into carbonic acid. If mixed with nitre, the potassa retains the carbonic acid, and the carbon may be thus easily estimated. If a mineral containing carbonic acid is heated, the gas escapes with effervescence, or a strong mineral acid as the hydrochloric will expel the acid with the characteristic effervescence.

(4.) _Phosphorus, Phosphoric Acid _(PO^{6}).--This acid occurs in a variety of minerals, associated with yttria, copper, uranium, iron, lead, manganese, etc. Phosphoric acid may be detected in minerals by pursuing the following process: dip a small piece of the mineral in sulphuric acid, and place it in the platinum tongs: this is heated at the point of the blue flame, when the outer flame will become colored of a greenish-blue hue. This color will not be mistaken for those of boracic acid, copper, or baryta. Some of the phosphoric minerals, when heated in the inner flame, will color the outer flame green.

If alumina be present with the phosphoric acid, the following wet method should be adopted for the detection of the latter: the substance should be powdered in the agate mortar with a mixture of six parts of soda, and one and a half parts of silica. The entire mass should now be placed on charcoal, and melted in the flame of oxidation. The residue should be treated with boiling water, which dissolves the phosphate and the excess of carbonate of soda, while the silicate of alumina, with some of the soda, is left. The clear liquor is now treated with acetic acid, and heated over the spirit-lamp, and a small portion of crystallized nitrate of silver added; a lemon-yellow precipitate of phosphate of silver is quickly developed. Previous to the addition of the nitrate, the liquor should be well heated; otherwise, a white precipitate of dipyrophosphate of silver will be produced.

If the examination be of any of the metallic phosphides, the substances should be powdered in the agate mortar, and fused with nitrate of potassa on the platinum wire; the fused mass should be treated with soda in the same manner as any substance containing phosphoric acid. The metal and the phosphorus are oxidized, while the phosphate of potassa is fused, and the metallic oxide separates.

(5.) _Sulphur_ (S).--Sulphur is found native in crystals It is frequently found associated with lime, iron, silica, carbon, etc., and combined extensively with metals.

The principal acid of sulphur (the sulphuric, SO^{3}) occurs combined with the earths, the alkalies, and the metallic oxides. Native sulphur is recognized, when heated upon charcoal, by its odor (sulphurous acid) and the blue color of its flame. The compounds of sulphur may be detected by several methods. If the substance is heated in a glass tube, closed at one end, the yellow sublimate of sulphur will subside upon the cool portions of the tube; if the substance should also contain arsenic, the sublimate will present itself as a light brown incrustation, consisting of the sulphide of arsenic.

If the assay is heated in the open glass tube, sulphurous acid will thus be generated; but, if the gas is too little to be detected by the smell, a strip of moistened litmus paper will indicate the presence of the acid.

The assay will give off sulphurous fumes if heated in the flame of oxidation.

If the powdered substance is fused with two parts of soda, and one part of borax, upon charcoal, the sulphide of sodium is formed. This salt, if moistened and applied to a polished silver surface, will blacken it. The borax serves no other purpose than to prevent the absorption of the formed sulphide of sodium by the charcoal. As selenium will blacken silver in the manner above indicated, the presence of this substance should be first ascertained, by heating the assay; when, if it be present, the characteristic horse-radish odor will reveal the fact.

Sulphuric acid may be detected by fusing the substance with two parts of soda, and one part of borax, on charcoal, in the flame of reduction; the mass must now be wetted with water, and placed in contact with a surface of bright silver; when, if sulphuric acid be present, the silver will become blackened.

Or the substance may be fused with silicate of soda in the flame of reduction. In this case, the soda combines with a portion of the sulphuric acid, which is then reduced to the sulphide, while the bead becomes of an orange or red color, depending upon the amount of the sulphuric acid present. If the assay should, however, be colored, then the previous treatment should be resorted to.

(6.) _Boron, Boracic Acid_ (BO^{3}).--This acid occurs in nature in several minerals combined with various bases, such as magnesia, lime, soda, alumina, etc. Combined with water, this acid exists in nature as the native boracic acid; this acid gives with test paper prepared from Brazil wood, when moistened with water, a characteristic reaction, for the paper becomes completely bleached. An alcohol solution turns curcuma test paper brown. Heated on charcoal, it fuses to a clear bead; but, if the sulphate of lime be present, the bead becomes opaque upon cooling.

The following reaction is a certain one: the substance is pulverized and mixed with a flux of four and a half parts of bisulphate of potassa, and one part of pulverized fluoride of calcium. The whole is made into a paste with water, and the assay is placed on the platinum wire, and submitted to the point of the blue flame. While the assay is melting, fluoboric gas is disengaged, which tinges the outer flame green. If but a small portion of boracic acid is present, the color will be quite evanescent.

(7.) _Silica, Silicic Acid_ (SiO^{3}).--This acid exists in the greatest plenty, forming no inconsiderable portion of the solid part of this earth. It exists nearly pure in crystallized quartz, chalcedony, cornelian, flint, etc., the coloring ingredients of these minerals being generally iron or manganese.

With _microcosmic salt_, silica forms a bead in the flame of oxidation which, while hot, is clear, while the separated silica floats in it. A platinum wire is generally used for the purpose, the end of it being first dipped in the salt which is fused into a bead, after which the silica must be added, and then the bead submitted to the flame of oxidation.

The silicates dissolve in soda but partially, and then with effervescence. If the oxygen of the acid be twice that of the base, a clear bead will be obtained that will retain its transparency when cold. If the soda be added in small quantity, the bead will then be opaque. In the first instance, a part of the base which separates is re-dissolved, and, therefore, the transparency of the glass; but, if too large a quantity of the soda is added, the separation of the base is sufficient to render the assay infusible.

(8.) _Chlorine_ (Cl).--Chlorine exists in nature always in combination, as the chlorides of sodium, potassium, calcium, ammonium, magnesia, silver, mercury, lead, copper, etc.

The chlorine existing in metallic chlorides may be detected as follows: the wet way may be accomplished in the following manner. If the substance is insoluble, it must be melted with soda to render it soluble; if it be already soluble it must be dissolved in pure water, and nitrate of silver added, when the one ten-thousandth part of chlorine will manifest its presence by imparting a milky hue to the fluid.

By the blowpipe, chlorine may be detected in the following manner: Oxide of copper is dissolved in microcosmic salt on the platinum wire in the flame of oxidation, and a clear bead is obtained. The substance containing the chlorine is now added, and heat is applied. The assay will soon be enveloped by a blue or purplish flame. As none of the acids that occur in the mineral kingdom give this reaction, chlorine cannot be confounded with them, for those which impart a color to the flame, when mixed with a copper salt, will not do so when tested in the microcosmic salt bead as above indicated.

If the assay is soluble in water, the following method may be followed: a small quantity of sulphate of copper or iron is dissolved; a few drops of the solution is placed upon a bright surface of silver, and the metallic chloride added; when, if chlorine is present, the silver is blackened. If the chloride is insoluble in water, it must be rendered soluble by fusion upon a platinum wire with soda, and then treated as above.[2]

[2] Plattner.

(9.) _Bromine_ (Br).--The bromide of magnesium and sodium exists in many salt springs, and it is from these that the bromine of commerce is obtained. The metallic bromides give the same reactions on silver with the microcosmic bead and copper salt as the metallic chlorides. The purplish color which, however, characterizes the chlorides, is more inclined to greenish with the bromides. If the substance be placed in a flask or glass tube, and fused with bisulphate of potassa, over the spirit-lamp, sulphurous gas and bromine will be eliminated. Bromine will be readily detected by its yellow color and its smell. Bromine may be readily detected by passing a current of chlorine through the fluid, after which ether is added and the whole is agitated. The ether rises to the top, carrying with it the bromine in solution; after being withdrawn, this ether is mixed with potassa, by which the bromide and bromate of potassa are formed. The solution is evaporated to dryness, the residue is fused in a platinum vessel, the bromate is decomposed, while the bromide remains; this must be distilled with sulphuric acid and the binoxide of manganese. A red or brown vapor will then appear, indicating the presence of bromine; this vapor will color starch paste--which may be put in the receiver on purpose--of a deep orange color.

If, to a solution containing a bromide, concentrated sulphuric or nitric acid be added, the bromine is liberated and colors the solution yellow or red. The hypochlorites act in the same manner. The bromine salts are coming into use extensively in photography, in consequence of their greater sensitiveness to the action of light than the chlorides alone.

(10.) _Iodine_ (I).--This element occurs in salt-springs, generally combined with sodium; it also exists in rock-salt; it has likewise been found in sea-water, also in a mineral from Mexico, in combination with silver, and in one from Silesia, in combination with zinc. As sea-water contains iodine, we would consequently expect to find it existing in the sea-weeds, and it is generally from the ashes of these that it is obtained in commerce.

When the metallic iodides are fused with the microcosmic salt and copper, as previously indicated, they impart a green color to the flame. This color cannot be mistaken for the color imparted to the flame by copper alone. When the metallic iodides are fused in a glass tube, closed at one end, with the bisulphate of potassa, the vapor of iodine is liberated, and may be recognized by its characteristic color. Those mineral waters containing iodine can be treated the same as for bromine, as previously indicated, while the violet-colored vapor of the iodine can be easily discerned. The nitrate of silver is the best test for iodine, the yellow color of the iodide of silver being not easily mistaken, while its almost insolubility in ammonia will confirm its identity. The chloride of silver, on the contrary, dissolves in ammonia with the greatest facility.

The reactions of iodine are similar to those of bromine with concentrated sulphuric acid and binoxide of manganese, and with nitric acid: The iodine is released and, if the quantity be not too great, colors the liquid brown. If there be a considerable quantity of iodine present, it is precipitated as a dark colored powder. Either of these, when heated, gives out the violet-color of the iodine.

With starch paste free iodine combines, producing a deep blue compound. If, however, the iodine be in very minute quantity, the color, instead of being blue, will be light violet or rose color.

If to a solution of the sulphate of copper, to which a small portion of sulphurous acid has been added, a liquid containing iodine and bromine is poured in, a dirty, white precipitate of the subiodide of copper is produced, and the bromine remains in the solution. The latter may then be tested for the bromine by strong sulphuric acid.

(11.) _Fluorine_ (Fl).--This element exists combined with sodium, calcium, lithium, aluminium, magnesium, yttrium, and cerium. Fluorine also exists in the enamel of the teeth, and in the bones of some animals. This element has a strong affinity for hydrogen, and, therefore, we find it frequently in the form of hydrofluoric acid. Brazil-wood paper is the most delicate test for hydrofluoric acid, which it tinges of a light yellow color. Phosphoric acid likewise colors Brazil paper yellow, but as this acid is not volatile at a heat sufficient to examine hydrofluoric acid, there can be no mistake. If the substance is supposed to contain this acid, it should be placed on a slip of glass, and moistened with hydrochloric acid, when the test paper may be applied, and the characteristic yellow color will indicate the presence of the fluorine.

As hydrofluoric acid acts upon glass, this property may be used for its detection. The substance may be put into a glass tube, and sulphuric acid poured upon it in sufficient quantity to moisten it; a slight heat applied to the tube will develop the acid, which will act upon the glass of the tube. If the acid is retained in the mineral by a feeble affinity, and water be present, a piece of it may be put in the tube and heated, when the acid gas will be eliminated. The test paper will indicate its presence, even before it has time to act upon the glass. If the temperature be too high, fluosilicic acid is generated, and will form a silicious incrustation upon the cool portion of the tube.

If the fluorine is too minute to produce either of the above reactions, then the following process, recommended by Plattner, should be followed: the assay should be mixed with metaphosphate of soda, formed by heating the microcosmic salt to dull redness. The mass must then be placed in an open glass tube, in such a position that there will be an access of hot air from the flame. Thus aqueous hydrofluoric acid is formed, which can be recognized by its smell being more suffocating than chlorine, and also by the etching produced by the condensation of vapor in the tube. Moist Brazil paper, applied to the extremity of the tube, will be instantly colored yellow.

Merlet's method for the detection of this acid is the following:[3] Pulverize the substance for examination, then triturate it to an impalpable powder, and mix it with an equal part of bisulphate of potassa. Heat the mass gradually in a moderately wide test-tube. The judicious application of heat must be strictly observed, for if the operator first heats the part of the tube where the assay rests, the whole may be lost on account of the glass being shattered. The spirit-flame must be first applied to the fore part of the tube, and then made to recede slowly until it fuses the assay. After the mixture has been for some time kept in a molten state, the lamp must be withdrawn, and the part containing the assay severed with a file. The fore part of the tube must then be well washed, and afterwards dried with bibulous paper. Should the fluorine contained in the substance be appreciable, the glass tube, when held up to the light, will be found to have lost its transparency, and to be very rough to the touch.

[3] Quoted by Plattner.

Great care should be observed not to allow this very corrosive acid to come into contact with the skin, as an ulcer will be the consequence that will be extremely difficult to heal.

When hydrofluoric acid comes in contact with any silicious substance, hydrofluosilicic acid gas is always formed.

(12.) _Selenium_ (Se).--This element occurs in combination with lead as the selenide, and with copper as the selenide of copper. It exists also combined with cobalt and lead, as the selenide of these metals; also as the selenide of lead and mercury.

The smallest trace of selenium may be detected by igniting a small piece of charcoal in the flame of oxidation, when the peculiar and unmistakable odor of decayed horse-radish will indicate the presence of that element. An orange vapor is eliminated if the selenium be present in any quantity, while there is an incrustation around the assay of a grey color, with a metallic lustre. This incrustation frequently presents a reddish-violet color at its exterior edges, often running into a deep blue. If a substance containing selenium be placed in a glass tube, closed at one end, and submitted to heat, the selenium is sublimed, with an orange-colored vapor, and with the characteristic odor of that substance. Upon the cool portions of the tube a steel-grey sublimate is deposited, and, beyond that, can be discerned small crystals of selenic acid. If the mineral be the seleniferous lead glance, sulphurous acid gas will be given off, and may be detected by the smell, or by a strip of moistened litmus paper.

If arsenic is present, heating upon charcoal will quickly lead to the determination of the one from the other.

* * * * *

TABULAR STATEMENT OF THE REACTIONS OF MINERALS BEFORE THE BLOWPIPE.

In PART THIRD of this work, commencing at page 109, the student will find a sufficiently explicit description of the blowpipe reactions of those principal substances that would be likely to come beneath his attention. The following tabular statement of those reactions--which we take from Scheerer and Blanford's excellent little work upon the blowpipe--will be of great benefit, as a vehicle for consultation, when the want of time--or during the hurry of an examination--precludes the attentive perusal of the more lengthy descriptions in the text.

In the examination of minerals, before the student avails himself of the aid of the blowpipe, he should not neglect to examine the specimen rigidly in relation to its physical characters, such as its hardness, lustre, color, and peculiar crystallization. It is where the difference of two minerals cannot be distinguished by their physical appearance, that the aid of the blowpipe comes in most significantly as an auxiliary. For instance, the two minerals molybdenite and graphite resemble each other very closely, when examined in regard to their physical appearance, but the blowpipe will quickly discriminate them, for if a small piece of the former mineral be placed in the flame of oxidation, a bright green color will be communicated to the flame beyond it, while in the latter there will be no color. Thus, in a very short time, these two minerals can be distinguished from each other by aid of the blowpipe, while no amount of physical examination could determine that point. The blowpipe is equally an indispensable instrument in the determination of certain minerals which may exist in others as essential or non-essential constituents of them. For instance, should a minute quantity of manganese be present in a mineral, it must be fused with twice its bulk of a mixture of two parts of carbonate of soda, and one part of the nitrate of potassa, in the flame of oxidation upon platinum foil. The manganate of soda thus formed will color the fused mass of a bluish-green tint.

Or a slight quantity of arsenic may be discerned by the following process recommended by Plattner:[4] one grain of the finely pulverized metal is mixed with six grains of citrate of potassa, and slowly heated on the platinum spoon. By this means the metals are oxidized, while the arseniate of potassa is obtained. Then boil the fused mass in a small quantity of water in a porcelain vessel till all tho arseniate is dissolved. The metallic oxides are allowed to subside, and the above solution decanted off into another porcelain vessel. A few drops of sulphuric acid are added, and the solution boiled to expel the nitric acid, after which it is evaporated to dryness. In this operation, the sulphuric acid should be added only in sufficient quantity to drive off the nitric acid, or, at the utmost, to form a bisulphate with the excess of potassa. When dry, the salt thus obtained is pulverized in an agate mortar, and mixed with about three times its volume of oxalate of potassa, and a little charcoal powder. The mixture is introduced into a glass bulb having a narrow neck, and gently warmed over a spirit-lamp in order to drive off the moisture, which must be absorbed by a piece of blotting-paper in the neck of the bulb. After a short time, the temperature is increased to a low red heat, at which the arsenious acid is reduced and the metallic arsenic sublimed, and which re-condenses in the neck of the bulb. If there the arsenic be so small in quantity as to exhibit no metallic lustre, the neck of the bulb may be cut off with a file immediately above the sublimate, and the latter exposed to the flame of the blowpipe, when the arsenic is volatilized, and may be recognized by its garlic odor.

[4] Quoted by Scheerer.

If the presence of cadmium is suspected in zinc-blende, it may be detected by fusing a small piece of the blende upon charcoal in carbonate of soda. The peculiar bright yellow sublimate of the oxide of cadmium, if it be present, will not fail to indicate it. This incrustation can be easily distinguished from that of zinc. Thus, with the three illustrations we have given, the student will readily comprehend the great utility of the blowpipe in the examination of minerals.

Although the following tables were not arranged especially for the last part of this work, still this arrangement is so good that by their consultation the student will readily comprehend at a glance what requires some detail to explain, and we feel no hesitation in saying that, although they are not very copious, they will not fail to impart a vast amount of information, if consulted with any degree of carefulness.

The minerals given are such as are best known to English and American mineralogists under the names specified. For more detailed reactions than could be crowded into a table, the student will have to consult the particular substance as treated in Part Third. If this part is perused carefully previous to consulting the tables, these will be found eminently serviceable as a refresher of the memory, and may thus save much time and trouble.

And, finally, we would certainly recommend the student, after he shall have gone through our little volume (if he is ambitious of making himself a thorough blowpipe analyst), to then take up the larger works of Berzelius and Plattner, for our treatise pretends to nothing more than a humble introduction to these more copious and scientific works.

* * * * *

Mineral. Diamond

Formula. C

Behavior

in glass-bulb. --

on platinum foil. In fine powder is slowly consumed without
residue in a strong oxidizing Flame.

* * * * *

Mineral. Graphite

Formula. C with some iron silica, etc.

Behavior

in glass-bulb. Generally gives off water.

on platinum foil. Is slowly consumed leaving more or less ash,
principally Fe^{2}O^{3}.

* * * * *

Mineral. Anthracite

Formula. C + x[.H]

Behavior

in glass-bulb. Evolves water.

on platinum foil. Is slowly consumed with the exception of a small
quantity of ash.

* * * * *

Mineral. Wallsend-coal

Formula. C, H, O, S and ash.

Behavior

in glass-bulb. Intumesces and gives off water and tarry matters
which partly condense in bulb, and leave a
porous coke.

on platinum foil. Takes fire under blowpipe flame, and burns with
a smoky flame, depositing much soot and leaving
a porous cinder which burns slowly and leaves a
small ash.

* * * * *

Mineral. Cannel-coal

Formula. C, H, N, O, S and ash.

Behavior

in glass-bulb. As the preceding but gives off more tar.

on platinum foil. Similar to the preceding. If held to the
lamp-flame, takes fire and burns for some
seconds.

* * * * *

Mineral. Brown-coal

Formula. C, H, N, O, S, and ash.

Behavior

in glass-bulb. Gives off much water and tar, and leaves a
porous cinder retaining the form of the original
fragment.

on platinum foil. Burns slowly and without flame, leaving some
ash.

* * * * *

Mineral. Asphaltum

Formula. C + H + O.

Behavior

in glass-bulb. Fuses with ease affording an empyreumatic oil
having an alkaline reaction, and combustible
gasses, and leaves a carbonaceous residue,
which is entirely consumed under the blowpipe
flame, except a little ash.

on platinum foil. Takes fire and burns with a bright flame and a
thick smoke.

* * * * *

Mineral. Elaterite

Formula. C + H.

Behavior

in glass-bulb. Fuses and gives off water having an acid
reaction, naphtha and a tarry fluid, which
chiefly condense in the neck of the bulb, and
leave a light, pulverulent carbonaceous residue.

on platinum foil. Fuses, takes fire, and burns with a smoky flame,
leaving a carbonaceous residue, which under the
blowpipe flame, is quickly consumed, with the
exception of the ashes.

* * * * *

Mineral. Hachettine

Formula. C + H.

Behavior

in glass-bulb. Fuses to a clear colorless liquid, which
solidifies on cooling and has a tallow-like
smell.

on platinum foil. Fuses, takes fire, and burns with a bright flame
until entirely consumed.

* * * * *

Mineral. Ozokerite

Formula. C + H.

Behavior

in glass-bulb. Fuses readily to a clear brown oily fluid, which
solidifies on cooling.

on platinum foil. As the preceding.

* * * * *

Mineral. Amber

Formula. C + H + O.

Behavior

in glass-bulb. Fuses with difficulty, and affords water, an
empyreumatic oil, and succinic acid which
condense in the neck of the bulb leaving a
shining black residue.

on platinum foil. Takes fire and burns with a yellow flame and a
peculiar aromatic odor.

* * * * *

Mineral. Mellite

Formula. [...Al][=M]^{3} + 15[.H]

Behavior

in glass-bulb. Gives off water. If heated to redness, is
carbonized, and gives a slight empyreumatic odor.

on platinum foil. On charcoal burns to a white ash, which moistened
with nitrate of cobalt and heated shows the
alumina reaction.

* * * * *

POTASH.

* * * * *

Mineral. Nitre

Formula. [.K][.....N]

Behavior

(1) in glass-bulb. Fuses readily to a clear liquid and with a
strong heat boils with the evolution of oxygen.

(2) in open tube. --

(3) on charcoal. Deflagrates leaving a saline mass, which is
absorbed into charcoal and gives a sulphur
reaction on silver.

(4) in forceps. On platinum wire fuses and colors the flame
violet more or less modified by lime and soda.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. --

(8) Special reactions. With bisulphate of potassa in the glass-bulb
evolves nitrous fumes.

* * * * *

Mineral. Polyhalite

Formula. [.K][...S]+[.Mg][...S]+2[.Ca][...S]+2[.H]

Behavior

(1) in glass-bulb. Gives off water.

(2) in open tube. --

(3) on charcoal. Fuses to a reddish bead, which in the reducing
flame solidifies and shrinks to a hollow crust.

(4) in forceps. On platinum wire fuses and colors the flame
yellow from a small quantity of soda.

(5) in borax. Dissolves with ebullition to a clear glass,
which is slightly colored by iron, and when
saturated become opaque on cooling.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses. The alkalies are absorbed by the charcoal
leaving the lime and magnesia infusible on the
surface.

(8) Special reactions. The alkaline mass when laid on silver gives a
sulphur reaction.

* * * * *

SODA.

* * * * *

Mineral. Rock-salt

Formula. NaCl.

Behavior

(1) in glass-bulb. Fuses to a clear liquid

(2) in open tube. --

(3) on charcoal. Fuses, is absorbed by the charcoal and partially
volatilized incrusting the charcoal around.

(4) in forceps. Fuses with great ease and colors the flame
yellow.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. --

(8) Special reactions. Gives the chlorine reactions.

* * * * *

Mineral. Natron

Formula. [.Na][..C] + 10[.H]

Behavior

(1) in glass-bulb. Fuses, with the evolution of water.

(2) in open tube. --

(3) on charcoal. Fuses, and is absorbed into the pores of the
charcoal.

(4) in forceps. Fuses and behaves as the preceding.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. --

(8) Special reactions. Dissolves in acid with violent effervescence.

* * * * *

Mineral. Soda-nitre

Formula. [.Na][.....N].

Behavior

(1) in glass-bulb. Fuses and if strongly heated evolves nitrous
fumes.
(2) in open tube.
--
(3) on charcoal.
Deflagrates and is absorbed into the charcoal.

(4) in forceps. Deflagrates on platinum wire, coloring the flame
yellow.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. --

(8) Special reactions. In a glass-bulb with bisulphate of potassa,
gives the NO^{5}-reaction.

* * * * *

Mineral. Glauber-salt

Formula. [.Na][...S] + 10[.H].

Behavior

(1) in glass-bulb. Fuses and gives off water having a neutral
reaction.

(2) in open tube. --

(3) on charcoal. Fuses, and is absorbed by the charcoal. The
saturated charcoal laid upon silver gives the
sulphur reaction

(4) in forceps. Fuses and colors the flame yellow.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. --

(8) Special reactions. Gives the SO^{3}-reaction.

* * * * *

Mineral. Glauberite

Formula. [.Na][...S] + [.Ca][...S].

Behavior

(1) in glass-bulb. Decrepitates with the evolution of more or less
water, and when strongly heated fuses to a clear
liquid.

(2) in open tube. --

(3) on charcoal. Fuses to a clear bead, then spreads out; the
soda is absorbed and the lime left on the
surface. Laid on silver, the fused mass gives a
sulphur reaction.

(4) in forceps. Fuses easily to a clear glass, coloring the
flame yellow.

(5) in borax. Fuses easily and gives the lime reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. As alone in charcoal.

(8) Special reactions. As in preceding.

* * * * *

Mineral. Borax

Formula. [.Na][...B]^{2}+10[.H].

Behavior

(1) in glass-bulb. Intumesces with the evolution of water, and
under a strong heat fuses.

(2) in open tube. --

(3) on charcoal. Intumesces and fuses to a clear bead more or
less colored by impurities.

(4) in forceps. As on charcoal.

(5) in borax. --

(6) in mic. salt. --

(7) with carb. soda. Fuses to a clear bead, which becomes crystalline
on cooling.

(8) Special reactions. Gives the boracic-acid-reaction.

* * * * *

Mineral. Cryolite

Formula. 3NaFl+Al^{2}Fl^{3}.

Behavior

(1) in glass-bulb. Decrepitates slightly and gives a trace of
water.

(2) in open tube. If heated so that the flame be allowed to play
up the tube upon the mineral, flourine is
evolved, which corrodes the interior of the
tube.

(3) on charcoal. Fuses to a limpid bead, which on cooling becomes
a white enamel. If heated for some time, it
bubbles, gives off fluorine and becomes
infusible.

(4) in forceps. Fuses, coloring the flame yellow.

(5) in borax. Dissolves to a clear bead, which is rendered
opaque by a large addition.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses to a clear bead, then spreads out on the
charcoal, the soda is absorbed, and an infusible
mass of alumina remains.

(8) Special reactions. If the alumina residue obtained be moistened
with cobalt solution and heated strongly, it
assumes a beautiful blue color.

* * * * *

BARYTA AND STRONTIA.

* * * * *

Mineral. Heavy-spar

Formula. [.Ba][...S].

Behavior

(1) in glass-bulb. Sometimes decrepitates and gives off more or
less water

(2) in open tube. --

(3) on charcoal. Fuses in the reducing flame.

(4) in forceps. Fuses with difficulty on edges. Colors the outer
flame green. In reducing flame forms BaS, which
fuses readily.

(5) in borax. Gives the baryta-reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses to a clear bead; then spreads out and is
absorbed into the charcoal. The fused mass laid
on silver gives the S-reaction.

(8) Special reactions. If fused with potassa on platinum, gives the
SO^{3}-reaction.

* * * * *

Mineral. Celestine

Formula. [.Sr][...S].

Behavior

(1) in glass-bulb. --

(2) in open tube. --

(3) on charcoal. Fuses to a milk-white bead.

(4) in forceps. Colors the flame crimson.

(5) in borax. Gives the strontia-reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Similar to the preceding.

(8) Special reactions. Similar to the preceding.

* * * * *

Mineral. Witherite

Formula. [.Ba][..C].

Behavior

(1) in glass-bulb. Decrepitates more or less and evolves Water.

(2) in open tube. --

(3) on charcoal. Fuses, effervesces, and is partially absorbed by
the charcoal.

(4) in forceps. Colors the outer flame intensely green.

(5) in borax. Dissolves with effervescence and gives the
baryta-reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses to a clear bead; then spreads out and
passes into the charcoal.

(8) Special reactions. In dilute HCl dissolves with much effervescence.

* * * * *

Mineral. Strontianite

Formula. [.Sr][..C].

Behavior

(1) in glass-bulb. Becomes opaque.

(2) in open tube. --

(3) on charcoal. As in the forceps.

(4) in forceps. Exfoliates and becomes arborescent. The
filaments glow brilliantly and fuse on the
point. Colors the flame brilliantly crimson.

(5) in borax. Resembles the preceding.

(6) in mic. salt. As in borax.

(7) with carb. soda. As the preceding.

(8) Special reactions. As the preceding.

* * * * *

Mineral. Barytocalcite.

Formula. [.Ba][..C] + [.Ca][..C].

Behavior

(1) in glass-bulb. As in the preceding.

(2) in open tube. --

(3) on charcoal. In powder frits together, but does not fuse.

(4) in forceps. Colors the flame green in the centre and red
towards the point.

(5) in borax. Dissolves with effervescence. In large
quantities gives a semi-crystalline bead.

(6) in mic. salt. As in borax, but the saturated bead is
milk-white.

(7) with carb. soda. Fuses, and is partially absorbed leaving the
lime on the surface.

(8) Special reactions. As witherite.

* * * * *

LIME.

* * * * *

Mineral. Gypsum

Formula. [.Ca][...S] + 2[.H].

Behavior

(1) in glass-bulb. Turns white, giving off water and being
converted into plaster of Paris.

(2) in open tube. --

(3) on charcoal. In the reducing flame forms CaS, which has an
alkaline reaction on test paper, and gives a
sulphur-reaction when laid on silver and
moistened.

(4) in forceps. Fuses with difficulty to a bead, coloring the
flame red.

(5) in borax. Dissolves to a clear bead, which gives the lime-
reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Behaves as lime. The alkaline mass laid on
silver and moistened gives the sulphur-reaction.

(8) Special reactions. Gives the sulphuric-acid reaction.

* * * * *

Mineral. Apatite { Cl Formula. [.Ca]{ -- +3[.Ca]^{3}[.....P] { Fl Behavior

(1) in glass-bulb. Occasionally decrepitates and gives off some
water.

(2) in open tube. --

(3) on charcoal. --

(4) in forceps. IV. Previously dipped in SO^{3} colors the flame
green, afterwards red.

(5) in borax. Dissolves easily and when in some quantity gives
an opaline bead.

(6) in mic. salt. Gives the lime-reaction.

(7) with carb. soda. Is infusible. The alkali is absorbed, leaving
the lime on the on the surface of the charcoal.

(8) Special reactions. With microcosmic salt and oxide of copper, gives
the chlorine-reaction. With microcosmic salt in
the open tube evolves fluorine.

* * * * *

Mineral. Pharmacolite

Formula. [.Ca]^{2}[.....As] + 6[.H].

Behavior

(1) in glass-bulb. Gives off water, and emits an arsenical odor.

(2) in open tube. --

(3) on charcoal. Fuses to an opaque bead and emits a strong smell
of arsenic.

(4) in forceps. Fuses to a translucent violet colored bead, the
color being due to cobalt. Colors the flame blue
at first, then faintly red.

(5) in borax. Dissolves readily to a bead strongly colored by
cobalt, which obscures the lime-reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses, and emits As. The alkali is then absorbed
by the charcoal, as in the preceding.

(8) Special reactions. --

* * * * *

Mineral. Calespar

Formula. [.Ca][..C].

Behavior

(1) in glass-bulb. Turns white and sometimes decrepitates. Strongly
heated loses CO^{2} and becomes caustic.

(2) in open tube. --

(3) on charcoal. Turns white, or brown if containing much iron or
manganese and glows brilliantly.

(4) in forceps. Glows brilliantly, coloring the flame red.
Becomes caustic and shows a strong alkaline
reaction.

(5) in borax. Dissolves with evolution of CO^{2} and when pure
gives the lime-reaction. The bead is generally
more or less colored by iron and manganese.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses, and behaves as other lime-salts.

(8) Special reactions. Dissolves with effervescence in cold HCl.

* * * * *

Mineral. Fluorspar

Formula. CaFl

Behavior

(1) in glass-bulb. Phosphoresces with various colors, when heated
in the dark.

(2) in open tube. --

(3) on charcoal. Fuses easily to a clear bead, which becomes opaque
on cooling, then loses fluorine, glows brilliantly
and becomes infusible.

(4) in forceps. As on charcoal. Colors the flame red.

(5) in borax. Gives the lime-reaction.

(6) in mic. salt. As in borax.

(7) with carb. soda. Fuses to a clear bead, opaque on cooling. With
an addition of the alkali behaves as lime.