THE CHEMISTRY DETECTIVE.

Star (Christchurch), Issue 16497, 6 August 1921, Page 15

THE CHEMISTRY DETECTIVE.

INVESTIGATION OF CRIME*

UNERRING LABORATORY WORK. New Scotland Yard may well be proud of its feats of detective skill; but at its best it is human and fallible. It is only the detective in the laboratory, on whom tho limelight seldom falls, who can boast that he never makes mistakes ; for with his test-tube:: and ro-agents he draws round the poisoner a net from which there is no escape. The cleverest brains are often baffled, but chemical science walks with remorseless steps to its inevitable goal. It seems magic, nothing else, thi9 detective work of the laboratory. Just tliink for a moment of the stupendous problems the chemical expert has to wrestle with. It is suspected that a man haß been poisoned. His duty is to determine what was the precise agent of death, and what was tho dose administered. The poison may come from tho whole domain of the vegetable and animal kingdoms and it must be traced and proved to the last fraction of a grain. But tho chemist smiles at such difficulties. If the poison is there, he knows that his skill will reveal the most microscopic trace of it. If there is but one-twenty-thousandth part- of a grain of opium, for example, a few drops of icdic acid will infallibly detect it l>y changing the solution containing it to a beautiful blue colour. Similarly, chloride of zinc will reveal morphia by a transformation to green. Half a grain of strychnine is a fatal dose; and before death this minute quantity of poison lias become mingled with every tissue of the body, which weigh, let us say, a hundredweight and a* half. Of arsenic two and a half grains may end a human life; and a sixteenth of a grain of prussic acid has proved fata!. DISCOVERING THE TRACES. There are, too, many poisons of which a deadly dose is still smaller. It seems inconceivable that even chemical magic can discover such infinitesimal quantities, distributed over a body, especially when, as often happens, that body ha.s long been lying underground in the process of decomposition. In one case, for example. areenic was found in the remains of a child after eight years’ burial, and another caso is on record where tho discovery was made fourteen years after death. Many poisons, such ns strychnine, belladonna and morphia, betray their action before death by violent spasms, a tendency to sleep or dilation of the pupils, thus simplifying the work of the chemist by suggesting tho particular medium employed. But in very many cases ho bias no such clue to aid him, and he must get to work to discovor by long process of tests arid eliminations which of dozens of poisons has been used. Bet us take an imaginary case for the purpose of illustration. Poison is suspected; but there is nothing whatever to suggest which poison it is. The first step of the analysis is to place the stomach of the victim, with its contents, into alcohol, and leave it there for forty-eight hours. The spirit is now carefully poured off and filtered, and tho liquid and residue are ready tor further examination. The £gsidno- by ,7 Ic.ohoi _uaul

tartaric acid, allowed to cool, and j once more filtered. The solution thu® obtained is shaken up—first with ether, then with chloroform and ether, which dissolve out all alkaloid®. On evaporation, now, a deposit is left. Tliis, the expert knows, j consists of one or inoco alkaloids. But which of them? Further tests follow. The deposit is mixed with a preparation of gold; the resultant deposit is weighed, burned and weighed again. Still the .goal is not reached. THE MYSTERIOUS RESIDUE. He now takes the mysterious residue. Ah 1 that peculiar tingling sonsation of the tongue! Nothing but aconite could cause it. He has found the poison at last. It is aconite, beyond a doubt. He tries a minute portion of it on a mouse. Within half an hour the mouse is dead. If his tests have revealed atropine, a name can easily bo given to it. If , a drop of a solution of only one part in 130,000 bo applied under the eyelid, the pupil will dilate immediately and conclusively. If arsenic is tho poison employed the victim's body will give up its secret infallibly to tho man in the laboratory, even, as wo have seen, after many years. The preservation I of the.body alone would Ijetray it; but ■ this is only a clue to his investigation . I Ho must submit the remains to a ' ' long series of tests—digesting small I portions in acid, adding re-agent, ; forming precipitates, heating in tubes, boiling with a piece of copper, and so on, until the crowning “ Marsh’s test 99 triumryliantly reveals the black spot of metallic arsenic deposited on a i piece of cold porcelain; and another j murderer is sent to tho gallons.