SCIENCE HELPS.

Auckland Star, Volume LXVIII, Issue 271, 15 November 1937, Page 5

SCIENCE HELPS.

CHEMICAL ANALYSES.

POLICE INVESTIGATORS.

WORK OF LABORATORY. Remarkable instances of the value of chemical analyses in carrying out jinvestigations for the Police Department jare given in the annual report of the {Dominion Laboratory.

In one investigation in Auckland,; numbers which had been filed off several! stolen bicycles were made visible by! Wising a solution of copper chloride in. ■hydrochloric acid containing 5 per cent ]of glycerine, the solution being kept' 'saturated by a freezing mixture until application. A small reservoir of dental sheet was made round the number and the solution applied for several short periods. Minute green patches on two overcoat [buttons of a person killed in a "hit and [run" case, and a dull streak on the mud- ' guard of the accused's motor truck were '(submitted for examination in Wellington.

It wag shown that the green patches! ion the buttons corresponded with the Igreen paint of a bent bar of the truck.; iScrapings from a number of the dull; streaks on the mudguard all gave the' characteristic smell of burning rubber when carefully heated over a small flame. |No similar smell was observed with scrapings from any other part of the mudguard. Smears were then made on' the mudguard with the rubber grip ofj deceased's motor cycle handle, andj scrapings from these all gave the smell I of burning rubber when heated. It wasj found, however, that after a period ofj .three weeks no such smell could be i obtained from these on the original • smear. This was probably due to oxidation changes in very thin deposits iof rubber. It wae therefore concluded • that the original smear could not have • been more than three weeks old when first examined.

Animal Poisoning. Four cases of animal poisouing were investigated in Christchurch. The most important of these investigations related to the death of 200 sheep. It was thought that they had been poisoned with strychnine, but an examination of two sheep negatived this. It was found that the feed had not been digested and had formed into hard lumps, causing an impacted condition of the bowels. This resulted from the dry condition of the pastures in use. When removed to green pasture, other sheep similarly ; affected rapidly recovered. j Friar's balsam was found to have ibeen used in a case of attempted suicide lin Christchurch. Glauber's salts, or sodium sulphate, a definitely mineral salt, was the main constituent of a ! "herbalist's" remedy.

Seven samples of liquor were examined, ale (1), hop beer (1), and cider (5). The eider, which contained 14 per cent to 20 per cent of proof spirit, was on open sale in single bottles in various .unlicensed premises in Christchurch. A preparation sold as aluminium solder in Wellington was found to be a mixture of 8 per cent aluminium powder with melted sulphur, and quite useless for the purpose of soldering aluminium. Pakapoo Secret Revealed. With a forged pakapoo ticket it was found possible from an examination of the ink and paper to discover the I method used by the accused. In the case of a forged receipt which iwas said to have been through the washtub. it was possible to show by means of absorption of eosin from ether by the paper fibres that as little as 30 seconds immersion in water would ;have removed the sizing of the paper.

Several cases of malicious poisoning of horses with strychnine have been investigated in Dunedin in recent years. During last year the strychnine in one case was associated with red dye. as required by the Poisons Act. 1934. This j would indicate that the poisoning was 'not accidental. j In a case of suspected incendiarism lin Auckland, several samples of fabric iwere found to have been soaked with kerosene.

The laboratory in Christchurch examined a total of 2635 samples during the year, 2444 being received from the Health Department. 147 from the Justice and Police Departments. 23 from •other (government Departments, and 22 | from local bodies and miscellaneous 1 sources.