_Marsh's Process._--Put pure distilled water into a Marsh's apparatus with metallic zinc and sulphuric acid. Hydrogen is set free, and should be tested by lighting the issuing gas and depressing over it a piece of white porcelain. If no mark appears, the reagents are pure, and the suspected liquid may now be added. The hydrogen decomposes a.r.s.enious acid, and forms a.r.s.eniuretted hydrogen. The gas carried off by a fine tube is again ignited. A piece of gla.s.s or porcelain held to the flame will have, if a.r.s.enic be present, a deposit on it having the following characters: In the centre a deposit of metallic a.r.s.enic, round this a mixture of metallic a.r.s.enic and a.r.s.enious acid, and outside this another ring of a.r.s.enious acid in octahedral crystals. The deposit is dissolved by a solution of chloride of lime, turned yellow by sulphide of ammonium after evaporation; on the addition of strong nitric acid, evaporated and neutralized with ammonia and nitrate of silver added, a brick-red colour is produced--a.r.s.eniate of silver.

_Reinsch's Process._--Boil distilled water with one-sixth or one-eighth of hydrochloric acid, and introduce a slip of bright copper. If, after a quarter of an hour's boiling, there is no stain on the copper, add the suspected liquid. If a.r.s.enic be present, it will form an iron-grey deposit. If this foil be dried, cut up, put in a reduction-tube, and heated, crystals of a.r.s.enious trioxide will be deposited on the cold part of the tube.

These tests are difficult to apply, but as a.r.s.enic is a ubiquitous poison, and as there are many sources of fallacy, it would be well, when possible, to obtain the services of an expert.

_Biological Test._--Put the substance to be tested into a flask with some small pieces of bread, sterilize for half an hour at 120 C. When cold, inoculate with a culture of _Penicillium brevicaule_, and keep at a temperature of 37 C. If a.r.s.enic is present, a garlic-like odour is noticed in twenty four hours, due to a.r.s.eniuretted hydrogen or an organic combination of a.r.s.enic. This test is delicate, and will detect 1/1000 of a milligramme, but it is not quant.i.tative.

=Other Preparations of a.r.s.enic.=--These are a.r.s.enite of potash (Fowler's solution), cacodylate of sodium, and a.r.s.enite of copper (Scheele's green), the last frequently used for colouring dresses and wall-papers.

Persons using these preparations may suffer from catarrhal symptoms, rashes on the neck, ears, and face, thirst, nausea, pain in stomach, vomiting, headache, perhaps peripheral neuritis and loss of patellar reflex. The cacodylates, although formerly employed in the treatment of phthisis, should be used with the utmost caution. The a.r.s.enites give the reactions of a.r.s.enious acid.

a.r.s.enic is eliminated not only by the kidneys and bowels, but by the skin, and in women by the menses. It may be detected in the sweat, the saliva, the bronchial secretion, and, during lactation, in the milk.

The sale of a.r.s.enic and its preparations to the public is properly hedged round with restrictions of all kinds. It is included in Part I.

of the Poisons and Pharmacy Act (8 Edward VII., c. 55). No a.r.s.enic may be sold to a person under age, nor may it be sold unless mixed with soot or indigo in the proportion of 1 ounce of soot or 1/2 ounce of indigo at the least to every pound of a.r.s.enic.

=a.r.s.eniuretted Hydrogen= (arsine, AsH_{3}) is an extremely poisonous gas, and is evolved in various chemical and manufacturing processes.

When damp, _Ferro-silicon_ evolves AsH_{3} and PH_{3}, both very lethal gases. _Ferrochrome_ is used in making steel, and it also evolves PH_{3}, and in such extreme dilution as 0.02 per cent. may cause death.

XXII.--ANTIMONY AND ITS PREPARATIONS

=Tartar Emetic= (tartarized antimony, pota.s.sio-tartrate of antimony) occurs as a white powder, or in yellowish-white efflorescent crystals.

Vinum antimoniale contains 2 grains to a fluid ounce of the wine.

_Symptoms._--Metallic taste, rapidly followed by nausea, incessant vomiting, burning heat and pain in stomach, purging. Dysphagia, sense of constriction in throat, intense thirst, cramps, faintness, profound depression; in fatal cases, giddiness and tetanic spasms. In _chronic poisoning_, nausea, vomiting and purging, weak pulse, loss of appet.i.te, debility, cold sweats, great prostration, progressive emaciation. The symptoms in chronic poisoning may simulate gastritis or enteritis.

Externally applied, it produces an eruption not unlike that of smallpox.

_Post-Mortem Appearances._--Inflammation, softening, and an aphthous condition of the throat, gullet, and stomach, the last reddened in patches. In chronic poisoning, inflammation also of caec.u.m and colon.

Brain and lungs may be congested. Decomposition is hindered for long.

_Treatment._--Promote vomiting by warm greasy water, or the stomach-tube may be used. Cinchona bark or any preparation containing tannin, as tea, decoction of oak bark, etc. Morphine to allay pain.

_Fatal Dose._--In an adult 2 grains (same as a.r.s.enic).

_Fatal Period._--Death follows in eight to twelve hours, from exhaustion.

_Method of Extraction from the Stomach._--The contents of the stomach or its coats should be finely cut up and boiled in water, acidulated with tartaric acid and subjected to dialysis, or strained and filtered. Pa.s.s hydrogen sulphide through the filtered or dialyzed fluid until a precipitate ceases to fall; collect the sulphide thus formed, wash and dry it. Boil the orange-coloured sulphide in a little hydrochloric acid. If the solution be now added to a large bulk of water, the white oxychloride is precipitated, which is soluble in tartaric acid and precipitated orange yellow with hydrogen sulphide. The chloride of bis.m.u.th is also precipitated white, but the precipitate is not soluble in tartaric acid, and the precipitate with hydrogen sulphide is black.

_Tests._--Soluble in water, but not in alcohol.

Heated in substance, it crepitates and chars; and if heat be increased, the metal is deposited. Treated with sulphuretted hydrogen, a characteristic orange-red sulphide is formed.

A drop of the solution evaporated leaves crystals, either tetrahedric, or cubes with edges bevelled off. Sulphuretted hydrogen pa.s.sed through gives the orange-red precipitate above named. Dilute nitric acid gives a white precipitate, soluble in excess, and also in tartaric acid. Marsh's and Reinsch's processes are applicable for the detection of antimony, but Reinsch's is the better. Reinsch's process gives a violet deposit instead of the black, l.u.s.trous one of a.r.s.enic.

=Chloride of Antimony= (b.u.t.ter of Antimony).--A light yellow or dark red corrosive liquid.

_Symptoms._--Violet corrosion and irritation of the alimentary ca.n.a.l, with the addition of narcotic symptoms. After death the mucous membrane of the entire ca.n.a.l is charred, softened, and abraded.

_Treatment._--As for tartar emetic; magnesia in milk.

XXIII.--MERCURY AND ITS PREPARATIONS

The most important salt of mercury, toxicologically, is corrosive sublimate. Other poisonous preparations are red precipitate, white precipitate, mercuric nitrate, the cyanide and pota.s.sio-mercuric iodide.

Calomel has very little toxic action. Metallic mercury is not poisonous, but its vapour is.

=Corrosive Sublimate= (perchloride of mercury) is in heavy colourless ma.s.ses of prismatic crystals, possessing an acrid, metallic taste. It is soluble in sixteen parts of cold and two of boiling water. Soluble in alcohol and ether, the latter also separating it from its solution in water.

_Symptoms_ come on rapidly. Acrid, metallic taste, constriction and burning in throat and stomach, nausea, vomiting of stringy mucus tinged with blood, tenesmus, purging. Feeble, quick, and irregular pulse, dysuria with scanty, alb.u.minous or b.l.o.o.d.y urine or total suppression.

Cramp, twitches and convulsions of limbs, occasionally paralysis. In poisoning from the medicinal use of mercury, there may be salivation, a coppery taste in the mouth, peculiar foetor of breath, tenderness and swelling of mouth, inflammation, swelling and ulceration of gums (cancrum oris), a blue line on the gums, and the loosening of teeth.

Mercury is less quickly eliminated from the body than a.r.s.enic. In chronic cases 'mercurialism,' 'hydrargyrism,' 'ptyalism,' or 'salivation,' including most of the symptoms enumerated above. May get _eczema mercuriale_ and periost.i.tis. Profound anaemia often a prominent symptom; neuritis not uncommon. If fumes of mercury inhaled, mercurial tremors develop.

_Post-Mortem Appearances._--Corrosion, softening, and sloughing ulceration of stomach and intestines. The mucous membrane of the oesophagus and stomach is often of a bluish-grey colour. The large intestine and r.e.c.t.u.m are often ulcerated and gangrenous. Inflamed condition of urinary organs, with contraction of the bladder.

_Treatment._--Encourage or produce vomiting. Alb.u.min, as white of egg, gluten, or wheat flour, is the best antidote. Demulcent drinks, milk, and ice. Stomach-tube to be used with care, owing to softened state of gullet and stomach.

_Fatal Dose._--Three grains in a child.

_Fatal Period._--Half an hour the shortest.

_Method of Extraction from the Stomach._--A trial test may be made of the contents of the stomach with copper-foil. If mercury is found, the contents of the stomach may be dialyzed, the resulting clear fluid concentrated and shaken with ether, which has the power of taking corrosive sublimate up, and thus separating it from a.r.s.enic and other metallic poisons. The ether allowed to evaporate will leave the corrosive sublimate in white silky-looking prisms. Suppose no mercury is found in the dialyzed fluid, owing to the fact that corrosive sublimate enters into insoluble compounds with alb.u.min, fibrin, mucous membrane, gluten, tannic acid, etc., we must dry the insoluble matter, and heat it with nitro-hydrochloric acid until all organic matter is destroyed and excess of nitric acid expelled. The residue dissolved in water, filtered, and tested with copper-foil, etc.

_Tests._--The following table gives the action of corrosive sublimate with reagents:

1. With iodide of pota.s.sium Bright scarlet colour.

2. With potash solution Bright yellow colour.

3. With hydrochloric acid and First a yellowish and then a black sulphuretted hydrogen colour.

4. Heated in a reduction-tube Melts, boils, is volatilized, and forms a white crystalline sublimate.

5. With ether Freely soluble; the ethereal solution, when allowed to evaporate spontaneously, deposits the salt in white prismatic crystals.

6. Heated with carbonate of Globules of metallic mercury are sodium in a reduction-tube produced.

A very simple process for detecting corrosive sublimate is to put a drop of the suspected solution on a sovereign and touch the gold through the solution with a key, when metallic mercury will be deposited on the gold.

XXIV.--LEAD AND ITS PREPARATIONS

=Acetate of Lead= (Sugar of Lead).--A glistening white powder or crystalline ma.s.s. Soluble in water, with a sweetish taste. It is practically the only lead salt which gives rise to acute symptoms, and only when taken in large doses.

_Symptoms._--Metallic taste, dryness in throat, intense thirst, vomiting, colicky pains, cramps, cold sweat, _constipation_ and scanty urine, severe headache, convulsions.