250 ROSACEA. 



page, in which 28 cwt. of ahnonds were treated, the yield of essential 

 oil amounted to 087 per cent. From data obligingly furnished to us 

 by Messrs. Herrings and Co. of London, who distill large quantities of 

 almond cake, it appears that the yield of essential oil is very variable. 

 The yearly averages as taken from the books of this firm, show that it 

 may be as low as 074, or as high as 1"67 per cent., which, assuming 57 

 pounds of cake as equivalent to 100 poimdsof almonds, would represent 

 a percentage from the latter of 0'42 and 0'95 per cent, respectively. 

 Mr, LTmney explains this enormous variation as due in part to natural 

 variableness in the different kinds of bitter almond, and in part to their 

 admixture with sweet almonds. He also states that the action of the 

 emulsin on the amygdalin when in contact with water, is extremely 

 rapid, and that 200 pounds of almond marc are thoroughly exhausted 

 by a distillation of only three hours. 



In the distillation, the hydrocyanic acid and bitter almond oil unite 

 into an unstable compound. From this, the acid is gradually set free, 

 and partly converted into cyanide of ammonium and formic acid. Sup- 

 posing bitter almonds to contain 3'3 per cent, of Amygdalin, they must 

 yield 0"2 per cent, of hydrocyanic acid. Pettenkofer obtained by 

 experiment as much as 0*25 per cent., Feldhaus (1863) 017 per cent. 



Some manufacturers apply bitter almond oil deprived of hydrocyanic 

 acid, but such purified oil is very prone to oxidation, unless carefully 

 deprived of water by being shaken with fused chloride of calcium. The 

 sp. gr. of the original oil is 1*061 — 1'065; that of the purified oil 

 (according to Umney) 1*049. The purification by the action of ferrous 

 sulphate and lime, and re-distillation, as recommended by Maclagan 

 (1853), occasions, we are informed, a loss of about 10 per cent. 



Bitter almond oil, C®H^(COH), being the aldehyde of benzoic acid, 

 C^H*(COOH), is easily converted in that acid by spontaneous or 

 artificial oxidation. The oil boils at 180° C. and is a little soluble in 

 water ; 300 parts of water dissolve one part of the oil. 



There are a great number of plants which if crushed, moistened with 

 water, and submitted to distillation, yield both bitter almond oil 

 and hydrocyanic acid. In many instances the amount of hydrocyanic 

 acid is so extremely small, that its presence can only be revealed by the 

 most delicate test, — that of Schonbein.^ 



Among plants capable of emitting hydrocyanic acid, probably always 

 accompanied with bitter almond oil, the tribes Prv/nece and Pomece of 

 the rosaceous order may be particularly mentioned. 



The farinaceous rootstocks of the Bitter Cassava, Manihot utilissinia, 

 Pohl, of the order Euphorbiacece, the source of tapioca in Brazil, have 

 long been known to yield hydrocyanic acid. 



A composite, Chardinict xeranthenioides Desf., growing in the Caspian 

 regions, has been shown by W. Eichler also to emit hydrocyanic acid.^ 

 The same has been observed by the French in Gaboon ^ with regard to 

 the fruits of Ximenia americana L. of the order OlacinecB, and the 



^ Applied in the following manner : — Let tense blue coloration in the presence of 



bibulous paper be imbued with a fresh tine- hydrocyanic acid. 



ture of the wood or resin of guaiacum, and ^ Btdl. de la Soc. imp. des nat. de Moscou, 



after drying, let it be moistened with a xxxv. (1862) ii. 444. 



solution composed of one part of sulphate ^ Exposition Univers. de 1867. — ProduUs 



of copper in 2000 of water. Such paper des Cohnies Frangaises, 92. 

 moistened with water will assume an in- 



