sufficient water and 30 c.c. of compound tincture of lavender to make 1000 c.c. The product is used in medicine under the name of Fowler's solution. Only the alkali arsenites are soluble in

water.

Cupric Arsenite, CuHASO, Scheele's Green, is an insoluble green powder used as a pigment.

Paris Green is a cupric aceto-arsenite made by boiling together solutions of copper acetate and arsenous oxide. It has the formula Cu(C2H3O2)2,3Cu(AsO2)2.

Arsenous oxide is one of the compounds most frequently employed as a poison. Its action may be deferred or neutralized by large doses of freshly precipitated ferric hydrate.

ARSENIC OXIDE AND ARSENATES.

Arsenic Oxide, АsО, Arsenic Pentoxide, is prepared by heating arsenic acid to low redness. It forms a white, fusible, glassy mass. By a strong heat it is converted into arsenous oxide and oxygen.

Arsenic Acid, HASO4, Orthoarsenic Acid, is obtained by long boiling of arsenous oxide and nitric acid. The solution is evaporated to a syrupy consistence, when crystals separate having the composition (H ̧ASO4)2.H2O. These crystals deliquesce in the air, and give up their water of crystallization at 100°. On heating to 180° they lose additional water and are converted into pyroarsenic acid, HAsО7, and at 200° a pearly, lustrous mass of meta-arsenic acid, HASO,, is formed.

Arsenic acid has some use as an oxidizer in the preparation of a number of the aniline colors.

Sodium Arsenate, Na,HASO,.7H2O. Sodii Arsenas, U. S. P. -This official salt may be prepared by neutralizing arsenic acid with sodium carbonate, but the process given by the Pharmacopoeia of 1870 is more economical; this consists in fusing together in a clay crucible 10 parts of arsenous oxide, 8.5 parts of sodium nitrate, and 5.5 parts of dried sodium carbonate. The fused product is poured while hot on a porcelain slab, dissolved in water, the solution filtered, and set aside to crystallize. The reaction involved is as follows:

AS2O3 + 2NaNO3 + Na2CO3 + H2O = 2Na2HASO4 + NgO3 + CO2.

The crystals should be kept in well-stoppered bottles; they effloresce in dry air, and are somewhat deliquescent in moist air.

Properties. Sodium arsenate occurs in colorless, transparent, monoclinic prisms. It is soluble in 4 parts of water at 15° and very soluble in boiling water; very sparingly soluble in cold alcohol, but dissolved by 60 parts of that liquid when boiling. On the application of a gentle heat the salt loses 5 molecules of

water, amounting to 28.8 per cent., at 148° the remainder of the water is given off, the salt melts, and at a red heat is converted into pyroarsenate.

Monobasic Sodium Arsenate, NaH2AsO.HO, and Tribasic Sodium Arsenate, Na,AsO4.12H2O, are known.

ARSENIC AND SULPHUR.

Arsenic Disulphide, AsËS, Realgar, is found native, crystallized in oblique rhombic prisms.

It is prepared by melting together 15 parts of metallic arsenic and 6.5 parts of sulphur, or by the sublimation of 4 parts arsenous oxide and 2 parts sulphur. The product occurs in red, glassy masses, translucent on the edges. It is insoluble in water, but is readily dissolved by the alkali sulphides.

Realgar is used as a coloring, in the manufacture of leather, and in the preparation of white or Indian fire. This consists of 24 parts saltpetre, 2 parts realgar, and 7 parts sulphur.

Arsenic Trisulphide, AsS, Orpiment.-Under the latter name this compound is found in nature, crystallized in lemon-colored, rhombic prisms. It is prepared by melting together 6 parts of metallic arsenic and 4 parts of sulphur, or by subliming a mixture of 4 parts of arsenous oxide and 3 parts of sulphur. This compound is also formed when hydrogen sulphide is passed into a hydrochloric acid solution of arsenous oxide. It is melted to a yellowish-red liquid when heated, and at 700° volatilizes without decomposition.

When dissolved in the alkali sulphides it forms arsenites and thioarsenites as follows:

2ASS34KOH = KASO2+ 3KASS + 2H2O.

On the addition of hydrochloric acid, the whole of the arsenic is reprecipitated as sulphide :

KASO + 3KASS+ 4HCI

=

2AS S3+ 4KCl + 2H2O.

The sulpharsenites or thioarsenites constitute a class of compounds which bear the same relation to arsenic trisulphide as the arsenites bear to arsenous oxide.

Arsenic Pentasulphide, As2S, is obtained by fusing arsenic trisulphide with the proper proportion of sulphur, or by precipitating a dilute solution of sodium or ammonium sulpharsenate with hydrochloric acid. It is a yellow, fusible mass which may be sublimed without decomposition, provided air is excluded.

The thioarsenates or sulpharsenates form a class of compounds, the members of which are prepared by dissolving arsenic pentasulphide in an alkali sulphide, or by precipitating an arsenate with hydrogen sulphide.

THE DETECTION OF ARSENIC IN ANIMAL TISSUES.

On account of the ease with which it may be obtained and the certainty of its action, arsenic figures in more cases of poisoning, both accidental and intentional, than any other substance.

Where some of the powdered material is obtained from the stomach in a comparatively pure form, the identification of it is quite easy. It is simply necessary to employ the usual qualitative reactions. But oftener the poison has been absorbed by the system, and it is necessary to separate it from the tissues, or it is so intimately mixed with the contents of the stomach as to make any preliminary separation impossible. The stomach and its contents, and sometimes the other organs, are cut finely and triturated in a porcelain mortar until a uniform mass is obtained. This is then placed in a clean porcelain evaporating dish, and an equal volume of hydrochloric acid, having a specific gravity of 1.12, is added. The whole is heated on a water-bath, and every five minutes from one to two grammes of potassium chlorate are added. This is continued until a thin, yellowish liquid is obtained; after the addition of a few more grammes of the chlorate, the heat is continued until all odor of chlorine has disappeared. The liquid is filtered, warmed to 70°, and treated for a considerable time. with hydrogen sulphide. This sulphide may be collected, washed, dissolved, and detected by the usual arsenic reagents and tests as described in Part V. of this work. The method as given serves for the separation of a number of other metals that are sometimes used as poisons, and they may then be detected by the appropriate tests.

It is of the greatest importance to employ in this operation dishes and reagents that are absolutely free from the presence of traces of contamination. Therefore a blank experiment should first be carried out to prove the absence of impurities.

ANTIMONY (Stibium).

Symbol, Sb. Atomic Weight, 119.6. Valence, III and V. History. Although long before his time the ores of antimony, and probably the metal itself, were known to the alchemists of the East, the initiative step to the present knowledge of the element was reserved for Basil Valentine, who about the middle of the fifteenth century prepared and described not only the metal, but also a number of its compounds. At the same time he pointed out the value of the metal for the preparation of medi

cines and of alloys. A century later, however, Libavius confounded antimony with bismuth.

In the early part of the present century, Thénard, Proust, and particularly Berzelius, added to the positive literature of this metal. The names given to the element at present are the Chaldean term, stibium, and the Latin title, antimonium, both of which were applied to the native sulphide until the time of Lavoisier.

Occurrence. The chief source of antimony is the mineral stibnite, SbSg, which has been known since early history, but the metal also occurs directly combined with arsenic, nickel, and silver; and, though infrequently and in small quantities only, antimony is found in the free state associated with the preceding forms. As oxide, Sb,Og, we have the element occurring as octohedral crystals, senarmontite, and in rhombic prisms, valentinite. Of other antimony ores may be mentioned those in which the trisulphide, SbS,, forms thio-antimonates, or the so-called sulphosalts, with the sulphides of such metals as copper, iron, lead, and silver, in which arsenic often replaces part of the antimony.

Stibnite is found extensively in Canada and in Hungary; considerable antimony ore enters commerce from Cornwall, Algiers, Borneo, Nevada, South America, and New Brunswick.

Preparation. To separate antimony from the accompanying minerals advantage is taken of the easy fusibility of the sulphide, which is heated in vertical cylinders having holes at the bottom for the egress of the molten sulphide; or this preliminary fusion is carried on in reverberatory furnaces. To obtain the metal, the purified sulphide formed as above described is either fused with metallic iron,

or is roasted to form oxide, which is afterwards reduced with charcoal and sodium carbonate, or with crude tartar, as follows: 2Sb2S3 + 3C + 6Na2CO3 2Sb2+ 9CO2 + 6Na,S. The availability of the reactions of both methods was known to Basil Valentine.

=

The process employed in England, where much of the antimony of commerce is prepared, comprises three successive stages, -viz., "singling," which consists in melting the sulphide with one-half its weight of scrap-iron for an hour and a half in plumbago crucibles; "doubling," whereby the metallic antimony, which was separated from the slag of iron sulphide formed in the

first operation, is fused for the same time with 2.5 per cent. each of sodium sulphate and a slag consisting principally of pearl-ash; and “melting for stove-metal" with a previously used slag of the last substance and an additional quantity of fresh pearl-ash for a similar period.

merce.

The metal is then poured into square moulds, its surface covered with slag, and the molten mass allowed to cool slowly to insure the peculiar crystalline structure which is required in comThe antimony so obtained may contain arsenic, from which it is freed by fusion with sodium carbonate and potassium nitrate, sometimes with the addition of a small quantity of antimony trisulphide, and subsequent reduction of the lixiviated mass by charcoal and sodium carbonate.

Properties.-Antimony is a lustrous, silver-white metal, more basic than arsenic but less so than bismuth. It is harder than the last metal, and like it crystallizes in obtuse rhombohedra, a mass of which exhibits a granular or a coarsely laminated, fernmarked, crystalline fracture, according as it is rapidly or slowly cooled. This structure determines the great brittleness of the metal. Antimony has a specific gravity of 6.7, is scarcely tarnished by air, melts at 432°, volatilizes at a bright red-heat, and can be distilled in hydrogen at a white-heat. On charcoal, before the blow-pipe it melts and evolves white fumes of trioxide, and, if the globule of molten metal is dropped from some height, it scatters in many small particles, which burn with a very bright flame to trioxide. At ordinary temperatures, cold water does. not act upon the element, which, however, at a red-heat decomposes steam. Hot, but not cold, hydrochloric and sulphuric acids, as also cold nitro-hydrochloric acid, dissolve antimony.

Nitric acid converts the metal into white antimony trioxide, Sb,O,, and antimonic acid, H,SbO; while solutions of the alkali hydrates produce no change. It combines directly with the halogens, and with sulphur, phosphorus, and arsenic. The existence of an amorphous allotropic modification of this element in the so-called explosive antimony obtained by the electrolysis of strong solutions of the compounds of the metal is still a matter of doubt.

Uses. From the metal a chloride, suitable for the preparation of some of the medicinal compounds, is prepared, but the largest amount of antimony is used in the trades and manufactures in the form of alloys or of compounds. Along with bismuth, antimony finds use in the construction of thermo-electric piles.