b. A solution of this ash, made by decoction with distilled water, should be only rendered slightly turbid by solutions of acetate of lead, bichloride of platinum, nitrate of baryta, nitrate of silver, oxalate of ammonia, and sulphuretted hydrogen.
c. If the beer contained common salt, the above solution will give a cloudy white precipitate with a solution of nitrate of silver. Each grain of this precipitate is equivalent to 1⁄2 gr. of common salt (nearly).
d. If GREEN COPPERAS (sulphate of iron) is present, ferridcyanide of potassium gives a blue precipitate, and ferrocyanide of potassium a bluish-white one, turning dark blue in the air; solution of chloride of barium gives a white precipitate, each grain of which, after being washed, dried, and ignited, represents 1·188 gr. of crystallised protosulphate of iron.
e. The ash, digested in water slightly acidulated with nitric acid, and then boiled, yields a solution which, when cold, gives a black precipitate with sulphuretted hydrogen, and a white one with dilute sulphuric acid when lead is present.
8. Wittstein’s method for the detection of ADULTERANTS in beer.[118] One litre of the suspected beer is evaporated by a moderate heat to the consistence of a thick syrup. This is poured into a tared glass cylinder capable of containing ten times its volume and weighed; five times its weight of 93° to 95° alcohol is added, and the whole frequently stirred, by means of a thick glass rod, during twenty-four hours.
[118] ‘Archiv der Pharmacie,’ January, 1876, (‘Pharm. Journal,’ 3rd series, v.)
By this means all the gum, dextrin, sulphates, phosphates, and chlorides are separated, and a comparatively small portion is obtained in solution. After clearing, this solution is decanted, the residue is again treated with fresh alcohol, the two products mixed, filtered, and the alcohol driven off by a gentle heat.
a. Of the syrupy residue left after this evaporation, a small portion is diluted with three times its bulk of water, and tested for picric acid, according to the directions already given.
b. The remaining largest portion of the syrup is agitated for some time with six times its weight of pure colourless benzol (boiling point 80° C.); this is decanted off, and the operation is repeated with fresh benzol, and
the two liquors, the first of which has become yellow, the second having scarcely changed colour, are evaporated at a gentle heat. The pale, yellow, resinous residue thus obtained may possibly contain brucine, strychnine, colchicine, or colocynthin. To ascertain this, three portions of the resin are placed on a porcelain capsule; one is treated with nitric acid (sp. gr. 1·33 to 1·40), another with concentrated sulphuric acid, and the third, after a few morsels of red chromate of potash have been added, also with sulphuric acid. A red colour, produced by the nitric acid, indicates brucine with certainty, and a violet colour colchicine; a red colour produced by sulphuric acid indicates colocynthin, and a purple violet, produced by sulphuric acid and bichromate of potash, reveals strychnine. Resin in which one or other of these colorations is produced possesses an extremely bitter taste; that in which the coloration does not take place is also bitter, but the bitterness recalls the well-known hop flavour.