Aids To Forensic Medicine And Toxicology Part 12

_General Reactions for Alkaloids._--(1) Wagner's reagent (iodine dissolved in a solution of pota.s.sium iodide) yields a reddish-brown precipitate; (2) Mayer's reagent (pota.s.sio-mercuric iodide) gives a yellowish-white precipitate; (3) phospho-molybdic acid gives a yellow precipitate; (4) platinic chloride, a brown precipitate; (5) tannic acid, etc.

In order to isolate an inorganic substance from organic matter, Fresenius's method is adopted. Boil the finely divided substance with about one-eighth its bulk of pure hydrochloric acid; add from time to time pota.s.sic chlorate until the solids are reduced to a straw-yellow fluid. Treat this with excess of bisulphate of sodium, then saturate with sulphuretted hydrogen until metals are thrown down as sulphides.

These may be collected and tested. From the acid solution, hydrogen sulphide precipitates copper, lead, and mercury, _dark_; a.r.s.enic, antimony, and tin, _yellowish_. If no precipitate, add ammonia and ammonium sulphide, iron, _black_, zinc, _white_, chromium, _green_, manganese, _pink_. The residue of the material after digestion with hydrochloric acid and pota.s.sium chlorate may have to be examined for silver, lead, and barium.

For the detection of minute quant.i.ties, the microscope must be used, and Guy's and Helwig's method of sublimation will be found advantageous.

Crystalline poisons may be recognized by their characteristic forms.

IX.--THE MINERAL ACIDS

These are sulphuric, nitric, and hydrochloric acids.

_Symptoms of Poisoning by the Mineral Acids._--Acid taste in the mouth, with violent burning pain extending into the oesophagus and stomach, and commencing immediately on the poison being swallowed; eructations, constant retching, and vomiting of brown, black, or yellow matter containing blood, coagulated mucus, epithelium, or portions of the lining membrane of the gullet and stomach. The vomited matters are strongly acid in reaction, and stain articles of clothing on which they may fall. There is intense thirst and constipation, with scanty or suppressed urine, tenesmus, and small and frequent pulse; the lips, tongue, and inside of the mouth, are shrivelled and corroded. Exhaustion succeeds, and the patient dies either collapsed, convulsed, or suffocated, the intellect remaining clear to the last. After recovering from the acute form of poisoning, the patient may ultimately die from starvation, due to stricture of the oesophagus, stomach, etc.

_Post-Mortem Appearances Common to the Mineral Acids._--Stains and corrosions about the mouth, chin, and fingers, or wherever the acid has come in contact. The inside of the mouth, fauces, and oesophagus, is white and corroded, yellow or dark brown, and shrivelled. Epiglottis contracted or swollen. Stomach filled with brown, yellow, or black glutinous liquid; its lining membrane is charred or inflamed, and the vessels are injected. Pylorus contracted. Perforation, when it takes place, is on the posterior aspect; the apertures are circular, and surrounded by inflammation and black extravasation. The blood in the large vessels may be coagulated.

Avoid mistaking gastric or duodenal ulcer, with or without perforation, for the effects of a corrosive poison.

_Treatment._--Calcined magnesia or the carbonate or bicarbonate of sodium, mixed with milk or some mucilaginous liquid, are the best antidotes. In the absence of these, chalk, whiting, milk, oil, soap-suds, etc., will be found of service. The stomach-pump should not be used. If the breathing is impeded, tracheotomy may be necessary.

Injuries of external parts by the acid must be treated as burns.

X.--SULPHURIC ACID

=Sulphuric Acid=, or oil of vitriol, may be concentrated or diluted. It is frequently thrown over the person to disfigure the features or destroy the clothes. Parts of the body touched by it are stained, first white, and then dark brown or black. The presence of corrosion of the mouth is as important as the chemical tests. Black woollen cloths are turned to a dirty brown, the edges of the spots becoming red in a few days, due to the dilution of the acid from the absorption of moisture; the stains remain damp for long, owing to the hygroscopic property of the acid.

_Method of Extraction from the Stomach._--The contents of the stomach or vomited matter should, if necessary, be diluted with pure distilled water and filtered. The stomach should be cut up into small pieces and boiled for some time in water. The solution, filtered and concentrated, is now ready for testing. Blood, milk, etc., may be separated by dialysis, and the fluid so obtained tested. A sulphate may be present.

Take a portion of the liquid, evaporate to dryness, and incinerate; a sulphate, if present, will be obtained, and may be tested.

_Caution._--Sulphuric acid may not be found even after large doses, due to treatment, vomiting, or survival for several days. In all cases every organ should be examined. Vomited matters and contents of stomach should not be mixed, but each _separately_ examined. This rule holds good for all poisons. On _cloth_ the stain may be cut out, boiled in water, the solution filtered, and tested with blue litmus and other tests.

_Post-Mortem Appearances._--Where the acid has come in contact with the mucous membranes there are dark brown or black patches. The stomach is greatly contracted, the summits of the mucous membrane ridges being charred and the furrows greatly inflamed; the contents are black or brown.

_Tests._--Concentrated acid chars organic matter; evolves heat when added to water, and sulphurous fumes when boiled with chips of wood, copper cuttings, or mercury. Dilute acid chars paper when the paper is heated; gives a white precipitate with nitrate or chloride of barium, and is entirely volatilized by heat. Dilute solutions give a white precipitate with barium nitrate, insoluble in hydrochloric acid even on boiling.

_Fatal Dose._--In an adult, 1 drachm.

_Fatal Period._--Shortest, three-quarters of an hour; average period from onset of primary effects, eighteen to twenty-four hours.

XI.--NITRIC ACID

=Nitric Acid=, or aqua fortis, is less frequently used as a poison than sulphuric acid. The fumes from nitric acid have caused death from pneumonia in ten or twelve hours.

_Method of Extraction from the Stomach._--The same as for sulphuric acid. In beer, etc., the mixture may be neutralized with carbonate of pota.s.sium, dialyzed, the fluid concentrated and allowed to crystallize, when crystals of nitrate of pota.s.sium may be recognized.

_Post-Mortem Appearance._--The mucous membranes are rendered yellow or greenish if bile be present; they are also thickened and hardened.

_Tests._--Concentrated acid gives off irritating orange-coloured fumes of nitric acid gas. When poured on copper, it gives off red fumes and leaves a green solution of nitrate of copper. It gives a red colour with brucine, turns the green sulphate of iron black, and with hydrochloric acid dissolves gold. A delicate test for the acid, free or in combination, is to dissolve in the suspected fluid some crystals of ferrous sulphate, and then to gently pour down the test-tube some strong sulphuric acid. Where the two liquids meet, if nitric acid be present, a reddish-brown ring will be formed. It turns the skin bright yellow, and does the same with woollen clothes, from the formation of _picric_ acid.

_Fatal Dose._--Two drachms.

_Fatal Period._--Shortest, one hour and three-quarters in an adult; in infants in a few minutes, from suffocation.

XII.--HYDROCHLORIC ACID

=Hydrochloric Acid=, muriatic acid, or spirit of salt, is not uncommonly used for suicidal purposes, being fifth in the list.

_Method of Extraction from the Stomach._--The same as for sulphuric acid. As hydrochloric acid is a const.i.tuent of the gastric juice, the signs of the acid must be looked for.

_Post-Mortem Appearances._--The mucous membranes are dry, white, and shrivelled, and often eroded.

_Tests._--The concentrated acid yields dense white fumes with ammonia.

When warmed with black oxide of manganese and strong sulphuric acid it gives off chlorine, recognized by its smell and bleaching properties.

Diluted it gives with nitrate of silver, a white precipitate, which is insoluble in nitric acid and in caustic potash, but is soluble in ammonia, and when dried and heated melts, and forms a h.o.r.n.y ma.s.s. Stains on clothing are reddish-brown in colour.

_Fatal Dose._--Half an ounce.

_Fatal Period._--Shortest, two hours; average, twenty-four hours. Death may occur after an interval of some weeks from destruction of the gastric glands and inability to digest food.

XIII.--OXALIC ACID

=Oxalic Acid= is used by suicides, though not often by murderers. The crystals closely resemble those of Epsom salts or sulphate of zinc; oxalic acid has been taken in mistake for the former. It is in common use for cleansing bra.s.s, in laundry work, for dyeing purposes, and especially for bleaching straw hats.

_Symptoms._--If a concentrated solution be taken, it acts as a corrosive, causing a burning acid, intensely sour taste, which comes on immediately, great pain and tenderness and burning at pit of stomach, pain and tightness in throat. Vomiting of mucus, b.l.o.o.d.y or dark coffee-ground matters, purging and tenesmus, followed by collapse, feeble pulse, cyanosis and pallor of the skin; also swelling of tongue, with dysphagia. In some cases cramps and numbness in limbs, pain in head and back, delirium and convulsions. May be teta.n.u.s or coma. If taken freely diluted, the nervous symptoms predominate, and may resemble narcotic poisoning. Sometimes almost instant death.

_Post-Mortem Appearances._--Mucous membrane of mouth, throat, and gullet, white and softened, as if they had been boiled; there are often black or brown streaks in it. Stomach contains dark, grumous matter, and is soft, pale, and brittle. Intestines slightly inflamed, stomach sometimes quite healthy.

_Treatment._--Warm water, then chalk, carbonate of magnesium, or lime-water, freely. Not alkalies, as the oxalates of the alkalies are soluble and poisonous. Castor-oil. Emetics, but not stomach-pump.

_Fatal Dose._--One drachm is the smallest, but half an ounce is usually fatal.