(d) Those which yield a larger quantity than 5 per cent., e.g.
| I. | |
| NH3 per cent. | |
| Solanine yields half its nitrogen as Ammonia | 0·98 |
| II. | |
| Morphia yields half its nitrogen as Ammonia | 2·98 |
| Codeine, ditto, ditto | 2·87 |
| Papaverine, ditto, ditto | 2·50 |
| Veratria, ditto, ditto | 2·87 |
| III. | |
| Atropia yields all its nitrogen as Ammonia | 5·73 |
| Narcotine, ditto, ditto | 4·11 |
| Strychnia yields half its nitrogen as Ammonia | 5·09 |
| Brucine, ditto, ditto | 4·32 |
| Aconite, ditto, ditto | 3·50 |
| Coneine, ditto, ditto | 4·60 |
| IV. | |
| Nicotine yields half its nitrogen as Ammonia | 10·49 |
IV. Dr Guy, as well as others, have made researches, having for their object the determination of the exact temperature at which the poisonous alkaloids melt and sublime. A very minute speck of the substance is placed on a porcelain plate or copper disc, and a square or oval of microscope-covering glass is placed over it, supported by a thin ring of glass or any other convenient substance.
Heat is then applied to the plate or copper, and the temperature, as indicated by a thermometer at which the substance fuses or volatilises, is carefully noted.
| Fahr. | Cent. | ||||
| Cantharidine sublimes as a white vapour without change of form or colour. | 212° | 100° | |||
| Sublime. | Melt. | ||||
| Fahr. | Cent. | Fahr. | Cent. | ||
| Morphine | Sublime, melt and yield carbonaceous residue. | 330° | 165° | 340° | 171° |
| Strychnine | 345° | 174° | 430° | 224° | |
| Melt. | Sublime. | ||||
| Fahr. | Cent. | Fahr. | Cent. | ||
| Aconitine | Melt, change colour, sublime, and deposit carbon. | 140° | 60° | 400° | 204° |
| Atropine | 150° | 66° | 280° | 138° | |
| Veratrine | 200° | 93° | 360° | 182° | |
| Brucine | 240° | 116° | 400° | 204° | |
| Digitalin | 310° | 154° | 310° | 154° | |
| Picrotoxin | 320° | 160° | 320° | 160° | |
| Solanine | 420° | 215° | 420° | 216° | |
Selmi’s method of extracting poisonous alkaloids in forensic investigations. The alcoholic extract of the viscera, acidified and filtered, is evaporated at 65° C., the residue taken up with water, filtered to separate fatty matters, and decoloured by means of basic acetate of lead, leaving the solution in contact with the air for 24 hours. It is then filtered, the lead precipitated by means of sulphuretted hydrogen, and the solution after concentration repeatedly extracted with ether. The ethereal solution is then saturated with dry carbonic anhydride, which generally causes a precipitate of minute drops adhering to the sides of the vessel, and containing some of the alkaloids. The ethereal solution is then poured into a clean vessel, mixed with about half its volume of water, and a current of carbonic anhydride
passed for about twenty minutes, which may cause the precipitation of other alkaloids not precipitated by dry carbonic anhydride. Usually the whole of the alkaloids present in the ether are thrown down by these means, but if not, the solution is dehydrated by agitation with Barium oxide, and then a solution of tartaric acid in ether added to the clear liquid, taking great care not to employ excess of acid. This throws down any alkaloid that may remain. In order to extract any alkaloids that may still remain in the viscera, they are mixed with Barium hydrate and a little water, and then agitated with purified amylic alcohol; the alkaloids may subsequently be extracted from the alcohol by agitation with very dilute sulphuric acid.
A knowledge of the different solubilities of the alkaloids will be found an important auxiliary in their analysis. The following is a summary of the relative solubility of the most important of them. The figures denote the number of parts of the liquid required for their solution:—
Absolute alcohol.—Strychnine insoluble; brucine soluble.
Amylic alcohol.—Solanine (1061); digitalin sparingly soluble; morphine (133); strychnine (122); veratrine, brucine, atropine, aconitine, and picrotoxin, freely soluble.