206 poisons : THEIR effects and detection. [§ 258. 
distilling a certain portion over. This Aqua Lauro-cerasi should contain 
0-1 per cent, by weight of HCN. 
§ 258. Poisoning by Prussic Acid. — Irrespective of suicidal or 
criminal poisoning, accidents from prussic acid may occur— 
1. From the use of the cyanides in the arts. 
2. From the somewhat extensive distribution of the acid, or 
rather of prussic-acid-producing substances, in the vegetable 
kingdom. 
1 . In the Arts. —In the galvanic silvering 1 and gilding of metals, 
photography, the colouring of black silks, the manufacture of Berlin 
blue, the dyeing of woollen cloth, and in a few other manufacturing 
processes, the alkaline cyanides are used, and not infrequently fumes of 
prussic acid developed. 
2. In the Animal Kingdom. —One of the myriapods ( Ghilognathen ) 
contains glands at the roots of the hairs, which secrete prussic acid ; 
when the insect is seized, the poisonous secretion is poured out from the 
so-called foramina repugnatoria. 
3. In the Vegetable Kingdom. —A few plants contain cyanides, and 
many contain amygdalin, or bodies formed on the type of amygdalin. In 
the presence of emulsin (or similar principles) and water, this breaks up 
into prussic acid and other compounds—an interesting reaction usually 
represented thus— 
C 20 H 27 NO 11 +2H 2 O -> CNH+C 7 H 6 0+2C 6 H 12 0 6 , 
1 equivalent of amygdalin— i.e. 457 parts—yielding 1 equivalent of 
CNH or 27 parts ; in other words, 100 parts of amygdalin yield theo¬ 
retically 5-90 parts of prussic acid, 2 so that, the amount of either being 
known, the other can be calculated from it. 
Dunstan and Henry 3 have discovered three glucosides :— 
“ dhurrin ” in the young plants of the great millet, Sorghum vulgare ; 
“ lotusin ” in Lotus arabiens, a legume indigenous to Egypt; and 
“ phaseo-lunatin ” in the beans of the wild Phaseolus lunatus. 
Lotusin , C 28 H 31 0 16 N, is a maltose-cyan-hydrin, one molecule yielding 
on hydrolysis 1 molecule of hydric cyanide, 2 of dextrose, and 1 of 
lotoflavin. 
1 The preparation used for the silvering of copper vessels is a solution of cyanide 
of silver in potassic cyanide, to which is added finely powdered chalk. Manipu¬ 
lations with this fluid easily develop hydrocyanic acid fumes, which, in one case 
related by Martin ( Aertzl . Intelligenzbl., p. 135, 1872), were powerful enough to 
produce symptoms of poisoning. 
2 According to Liebig and Wohler, 17 grms. of amygdalin yield 1 of prussic acid 
(i.e. 5-7 per cent.) and 8 of oil of bitter almonds. Thirty-four parts of amygdalin, 
mixed with 66 of emulsin of almonds, give a fluid equalling the strength of acid of 
most pharmacopoeias, viz. 2 per cent. 
3 Proc. Boy Soc., lxviii., 1901 ; lxxii., 1903. 
