[331] Dragendorff’s _Gerichtlich-chemische Ermittelung von Giften_, St. Petersburg, 1876, p. 141. I. The substance, in as finely-divided form as possible, is digested for a few hours in water acidified with sulphuric acid, at a temperature of 40° to 50°, and this operation is repeated two or three times, with filtering and pressing of the substances; later, the extracts are united. This treatment (if the temperature mentioned is not exceeded) does not decompose the majority of alkaloids or other active substances; but there are a few (_e.g._, solanine and colchicine) which would be altered by it; and, if such are suspected, maceration at the common temperature is necessary, with substitution of acetic for sulphuric acid.[332] [332] When blood is to be examined, it is better to dry it, and then powder and extract with water acidified with dilute sulphuric acid. However, if the so-called volatile alkaloids are suspected, this modification is to be omitted. II. The extract is next evaporated until it begins to be of a syrupy consistence; the residue mixed with three to four times its volume of alcohol, macerated for twenty-four hours at about 34°, allowed to become quite cool, and filtered from the foreign matters which have separated. The residue is washed with alcohol of 70 per cent. III. The filtrate is freed from alcohol by distillation, the watery residue poured into a capacious flask, diluted (if necessary) with water, and filtered. Acid as it is, it is extracted at the common temperature, with frequent shaking, by freshly-rectified petroleum ether; and, after the fluids have again separated, the petroleum ether is removed, carrying with it certain impurities (colouring matter, &c.), which are in this way advantageously displaced. By this operation ethereal oils, carbolic acid, picric acid, &c., which have not been distilled, besides piperin, may also be separated. The shaking up with petroleum ether is repeated several times (as long as anything remains to be dissolved), and the products are evaporated on several watch-glasses. RESIDUE OF PETROLEUM ETHER FROM THE ACID SOLUTION. 1. IT IS CRYSTALLINE. 2. IT IS AMORPHOUS. 3. IT IS VOLATILE, with a powerful odour; _ethereal oil, carbolic acid, &c._ A. _It is yellowish_, A. It is fixed. and with difficulty volatilised. α. The crystals are α. Concentrated sul- dissolved by concen- phuric acid dissolves trated sulphuric it immediately-- acid, with the pro- violet, and later duction of a clear greenish-blue. yellow colour, pass- _Constituents of the ing into brown and black hellebore._ greenish-brown. _Piperin._