Chemical Analysis.—The alkaloid may be extracted from organic admixture by the usual methods. Its reactions to special tests are as follows:
1. If nitric acid be added to the solid alkaloid, or in aqueous solution, a bright red colour is produced which changes to yellow on heating. The addition of stannous chloride or sulphide of ammonium to the acid solution after cooling changes it to violet; the colour is discharged by excess of the stannous chloride. If the red acid solution be largely diluted with water, a yellow precipitate falls, soluble in dilute hydrochloric acid. If the filtrate from the yellow precipitate be neutralised by ammonia and calcium chloride added, a precipitate of calcium oxalate forms, insoluble in acetic but soluble in hydrochloric acid. This reaction is peculiar to brucine.
2. With sulphuric acid and potassium bichromate a deep orange-red colour is produced.
3. Sulphomolybdic acid gives an orange-red or purplish-red colour, changing to blue.
4. Blyth‘s Test.—If methyl iodide be added to a solution of brucine in strong alcohol, circular rosettes of crystals form in a few minutes. Strychnine does not give this reaction.
Treatment.—Same as for strychnine.
CHAPTER XV
IRRESPIRABLE GASES
CARBON DIOXIDE
Circumstances under which it occurs accidentally.—Death may result where several persons are sleeping in the same room, and the ventilation is imperfect; from the admission of the vapour of charcoal into a room from an adjoining vent; or from incautiously sleeping in a brewery close to a vat in which fermentation is going on. Many deaths have occurred from this gas, due to the incautious descent into wells. It must also be borne in mind that death may result from the presence of this gas in an atmosphere which will permit the combustion of a candle. For a candle will burn in an atmosphere containing 25 per cent. of CO₂, whereas 5 per cent. will cause death. The burning of a candle is therefore no test of security from danger in an atmosphere where the presence of carbonic acid is suspected. Carbonic acid does not, as is generally supposed, sink to the lower portions of a room; and Dr. Taylor, from his experiments, states “that in a small and close room persons are liable to be suffocated at all levels, from the very equal and rapid diffusion of carbonic acid during combustion.”