Sweet almonds contain emulsin, but no amygdalin, hence give no HCN (see Tawell’s Trial, p. 40).
According to my own experiments, 837 sweet apples (apples weighing 135 pounds, pips about 5 oz.), would be required for a poisonous dose of HCN; whereas 130 bitter apples, weighing 18 pounds, and the pips about 2½ oz., would suffice. The pips of bitter apples are bigger, more numerous, and weigh about three times as much as those of sweet apples.
Among substances containing much more HCN, and actually poisonous on that account, are:—
| HCN. | ||||
| Crude bitter almond oil | 8 to 15 | per cent. | ||
| Bitter almond water | ¼ to 1 | ” | ||
| Cherry laurel oil | 2 to 3 | ” | ||
| ” | ” | water[21] | ¼ to ¾ | ” |
| Cluster cherry oil | 9 to 10 | ” | ||
(Allen, Comm. Org. Anal.) It is obvious that of fruits an impossibly large quantity must be eaten to produce any considerable amount of HCN. In Tawell’s trial, Mr. Cooper, the analyst, deposed that the seeds from 15 apples gave him an exceedingly small quantity of Prussian blue. Whereas, Henry Thomas, a druggist’s assistant, stated that “15 small apples gave 2¼ grains of silver cyanide” [equal to 0·46, or nearly ½ a grain, of anhydrous HCN, corresponding to 25 minims of B. P. acid, nearly a poisonous dose!] “This was done under the direction of a lecturer at the London Hospital.” A fair sample of the erroneous and bewildering evidence that is frequently offered in courts of justice.
Mr. Cooper also stated “there is a great difference between bitter and sweet apples; the bitter contain a great deal of prussic acid, the sweet, I believe, none at all!” This statement is misleading; no apples contain prussic acid, but all that I have met with will yield it by maceration, as all contain amygdalin. The highest class of eating apples, such as Newtown pippins, Ribstones, and Blenheims, contain only a minute trace. These have very few pips, 3 to 5 to each apple, while the bitter varieties, such as “winesours,” have 9 to 13 pips.
In the arts, cyanides are used in photography, dyeing, cleaning lace and metals, electro-plating, removing silver stains, &c. Their solutions may cause accidental poisoning, either by the fumes or by absorption through the skin, especially if the latter is abraded.
Hydrocyanic acid is also formed (1) in the preparation of nitrous ether (sweet spirit of nitre), (2) by distilling albumen, fibrin, casein, or gelatin, with sulphuric acid and bichromate of potash, or manganese peroxide, (3) by the dry distillation of albuminous bodies. It is hardly necessary to say that these formations could not occur in the ordinary methods of testing.
Tests: Preliminary.—It cannot be too strongly insisted that all operations for the detection of HCN should be carried out as soon after death as possible, on account of the loss from volatility, or from secondary changes. (See Sulphocyanides.)