a preliminary examination in the dry way, by which means approximate information as to its composition may be obtained; after this, it is dissolved and examined. The course of qualitative analysis, therefore, consists of three parts:

I. Preliminary examination in the dry way.

II. Solution, or conversion into the liquid form.
III. Analysis of the solution.

I. PRELIMINARY EXAMINATION.

This consists in an accurate observation, often by the aid of a lens or a microscope, of the physical properties of the substance, its form, color, hardness, gravity, and odor, and of its deportment at a high temperature, either alone, or in contact with some chemical compound which produces decomposition.

1. THE SUBSTANCE IS HEATED IN A DRY NARROW TUBE OPEN AT BOTH ENDS (Fig. 27).

(a) The substance remains unaltered; indicating absence of organic matter, of salts containing water of crystallization, and of volatile compounds.

FIG. 27.

() Non-volatile organic substances carbonize and blacken, evolving empyreumatic, inflammable gases.

(c) The substance fuses, expelling aqueous vapors, which condense in the cooler parts of the tube; indicating salts with water of crystallization (these will generally resolidify after the expulsion of the water), or decomposable hydrates, which often give off their water without fusing. The acid or alkaline reaction of the condensed vapors should be determined by means of litmus-paper.

(d) A change of color takes place; zine oxide assumes a yellow color while hot, which disappears again on cooling; mercuric oxide shows a transitory brown coloration, followed by the sublimation of metallic mercury; mercuric iodide sublimes with a yellow color; chromates, and the oxides of lead and bismuth are colored brown.

(e) Gases or fumes are evolved; iodine or bromine vapors would indicate their respective compounds, and may be recognized by the violet or brownish-red color and characteristic odor of the vapor; sulphur dioxide is often produced by the decomposition of sulphates; nitric peroxide arises from the decomposition of many nitrates, and is recognized by its brownish color and suffo

cating odor; cyanogen is recognized by its odor, and would indicate such cyanogen compounds as are decomposable by heat (mercuric cyanide); ammonia vapors may arise either from the decomposition of ammonium salts, cyanogen compounds, or from nitrogenous organic compounds; in the latter case carbonization takes place, and either cyanogen or empyreumatic fumes escape with the ammonia.

(f) Sublimates are formed by volatile substances, such as sulphur, ammonium salts, compounds of mercury, arsenic, and antimony, and some organic acids (benzoic, succinic, oxalic, salicylic, etc.). Sulphur sublimes in reddish-brown drops, which, upon cooling, assume a yellow or yellowish-brown color; metallic mercury forms globules, which are sometimes only distinguishable by the aid of a lens; mercuric chloride melts before volatilizing, and mercurous chloride sublimes without previously melting; when touched with a solution of potassium hydrate the sublimate assumes a yellow color with mercuric, a black one with mercurous salt; metallic arsenic forms the well-known mirror, arsenious acid small octahedral crystals, and the sulphides of arsenic a reddish-yellow, or, when cold, yellow sublimate; antimonious oxide melts first to a yellow liquid, and then sublimes in bright, shining needles.

2. THE SUBSTANCE IS MIXED WITH SODA-LIME, AND HEATED IN A DRY GLASS TUBE (Fig. 28).

The development of ammonia vapors will indicate ammonium salts, or nitrogenous compounds.

FIG. 28.

3. THE SUBSTANCE IS MIXED WITH DRIED SODIUM CARBONATE, AND HEATED ON CHARCOAL IN THE REDUCING FLAME OF

THE BLOWPIPE (Fig. 29).

(a) Fusion and absorption into the coal indicate alkalies, or their salts.

(b) An infusible white residue, either at once or after previous fusion in the water of crystallization, indicates compounds of

FIG. 29.

calcium, barium, strontium, magnesium, aluminium, zinc, or tin.

(c) A reduction to the metallic state takes place, without formation of a peripheric incrustation upon the charcoal. Compounds of tin, silver, and copper, give malleable shining scales. Compounds of iron, manganese, cobalt, and nickel, are reduced to a gray infusible powder; all visible

upon cutting the fuse from the coal, and triturating and levigating it in an agate mortar (Fig. 30).

FIG. 30.

(d) Reduction with incrustation: Antimony compounds give a brittle metallic globule and a white incrustation; bismuth, a brittle globule and a brown-yellow incrustation; lead, a malleable globule and a yellow incrustation; zinc and cadmium are not reduced, but give, the former, a white incrustation, not volatile in the oxidizing flame, the latter, a brown-red incrustation.

(e) Arsenic compounds evolve the smell of garlic.

(f) Borax and alum intumesce, and lose their water of crystal

lization.

(9) All sulphur compounds give an alkaline sulphide, which, when moistened upon a clean silver plate, produces a black stain, and with acids develops hydrogen sulphide.

(h) If deflagration takes place, nitrates, chlorates, iodates, or bromates are indicated.

4. THE SUBSTANCE, CONTAINED ON THE LOOPED END OF A MOUNTED PLATINUM WIRE (Fig. 31), IS HEATED IN THE

UPPER REDUCING PORTION OF THE NON-LUMINOUS GAS
FLAME.

(a) A violet color imparted to the flame indicates potassium salts. As this reaction may be perfectly concealed by the presence of sodium salts, the flame should be observed through blue glass.1

FIG. 31.

(2) A yellow color imparted to the flame indicates sodium salts. (e) The substance is moistened with hydrochloric acid, and the color of the flame observed; a purplish-red color indicates strontium, a carmine-red, lithium, and a yellowish-red color, calcium salts; a green coloration indicates either copper or barium salts, more evident with the former than with the latter.

(d) The substance is first heated to deprive it of moisture, then moistened with a drop of strong sulphuric acid, and the color of the flame observed; a green coloration may indicate phosphoric or boric acid, which, however, particularly when sodium compounds are present, is only of transient duration.

(e) A blue coloration imparted to the flame may indicate arsenic, antimony, or lead compounds.

5. A SMALL AMOUNT OF POWDERED BORAX IS MELTED ON THE LOOPED END OF A PLATINUM WIRE, BROUGHT IN CONTACT WITH A TRACE OF THE SUBSTANCE TO BE TESTED, AND HEATED:

(a) In the outer blowpipe flame, or in the lower oxidizing por tion of the non-luminous gas flame.

A blue glass or bead indicates cobalt.

An amethyst-red colored glass indicates manganese.

A green glass indicates chromium or copper (the copper bead becomes blue on cooling, the chromium bead yellowish-green). A brown-red glass indicates nickel or iron (the iron bead, when cold, is often of a yellowish color).

A yellow glass indicates uranium or lead.

1 The blue glass, which is tinted with cobalt monoxide, possesses the property of absorbing the yellow rays of light, and permits only the blue and violet rays of the spectrum to pass through it.

A colorless glass indicates molybdic acid, tin, antimony, and bismuth, as also the alkaline earths; the latter, however, becoming opaque on cooling.

(b) In the inner blowpipe flame, or in the lower reducing portion of the non-luminous gas-flame.

A blue glass indicates cobalt.

A yellow or brownish-red glass indicates copper or molybde

num.

A green glass indicates chromium, iron, or uranium.

A gray glass indicates nickel, bismuth, silver, or antimony.

A colorless glass indicates manganese, as also the alkaline earths; the latter showing the same behavior in both the reducing and the oxidizing flames.

The operation of reduction is usually more easily accomplished by the use of phosphorous salt, instead of borax; the former producing in the oxidizing flame with the oxides of manganese, cobalt, chromium, copper, iron, nickel, antimony, and molybdenum, and in the reducing flame with the oxides of cobalt, iron, uranium, chromium, copper, bismuth, and silver, the same results as with borax; the oxides of bismuth and silver, however, yield a yellow colored glass. With either phosphorous salt or borax, and heated in the oxidizing or reducing portion of the flame, silica and silicates produce a skeleton in the bead.

II. SOLUTION OF SOLID BODIES.

After having ascertained, by the preliminary examination, to what class of bodies the substance under consideration belongs, it has then to be brought into the liquid form-in other words, to be dissolved. The usual solvents which are employed are water, hydrochloric, nitric, and nitro-hydrochloric acids. The finely pow dered substance is first boiled with from 12 to 20 times its weight of distilled water, in order to ascertain its complete or partial solubility, or its insolubility therein. If it be not completely dissolved, the portion insoluble in water is collected upon a filter, and is then treated successively with dilute and concentrated hydrochloric acid; by this process carbonates evolve carbonic-acid gas, with effervescence; peroxides, chromates, and chlorates, evolve chlorine; cyanides give hydrocyanic acid; many sulphides, hydrogen sulphide; sulphites and hyposulphites, sulphurous acid.

If hydrochloric acid does not completely dissolve the substance, it generally effects the separation of one or more of its constituents; for this reason the solution should be separated from the residue and examined apart. The residue may consist of compounds undecomposable by hydrochloric acid, which existed in the original substance; or of insoluble compounds formed by the decomposition of the original substance by hydrochloric acid. Thus sulphur is separated from polysulphides, and pulverulent or gelatinous silica from silicates; or, if lead, silver, or mercurous