('(.^POUNDS OF CABBON WITH OXYGEN AND NITROGEN 403 



The salts MCN for instance, potassium, sodium, ammonium as 

 well as the salts M(CX) 2 for instance, barium, calcium, mercury are 

 soluble in water, but the salts of manganese, zinc, lead, and many others 

 are insoluble in water. They form double salts with potassium cyanide 

 and similar metallic cyanides, an example of which we will consider in 

 a further description of the yellow prussiate. Not only are some of 

 the double salts remarkable for their constancy and comparative 

 stability, but so also are the soluble salt HgC 2 N 2 , the insoluble silver 

 cyanide AgCN, and even potassium cyanide in the absence of water. 

 This salt, 46 when fused, acts as a reducing agent with its elements, K 

 and C, and oxidises when fused with lead oxide, forming potassium 

 cyanate, KOCN", which establishes the connection between HCN and 

 OHCN that is, between the nitriles of formic and carbonic acids 

 which connection is the same as between the acids themselves, because 

 formic acid, on oxidation, yields carbonic acid. The relation which 

 exists between hydrocyanic acid, metallic cyanides, and the salts of 

 cyanic acid, as well as between all the above-mentioned compounds, 

 may be expressed by granting the existence of a radicle in them con- 

 taining carbon and nitrogen cyanogen, CN. In this sense, prussic 

 acid is hydrocyanic acid, and cyanic acid a cyanogen hydroxide, in 

 exactly the same way as for chlorine we have hydrochloric acid, HC1, 

 and hypochlorous acid, C1OH. Free cyanogen ought to be represented 

 as prussic acid in which the hydrogen has been replaced by cyanogen, 

 (CN) 2 or CNC1S". This composition, judging from what has been 



tillation of certain vegetable substances. The so-called laurel water in particular enjoys 

 considerable notoriety from its containing hydrocyanic acid. It is obtained by the 

 steeping and distillation of laurel leaves. A similar kind of water is formed by the 

 infusion and distillation of bitter almonds. It is well known that bitter almonds are 

 poisonous, and have a peculiar characteristic taste. This bitter taste is due to the 

 presence of a certain substance called amygdalin, which can be extracted by alcohol. 

 This amygdalin decomposes in an infusion of bruised almonds, forming the so-called 

 bitter almond oil, glucose, and hydrocyanic acid : 



+ H 2 O = C 7 H 6 O + CNH + 2C 6 H 12 O 6 . 

 Amygdalin in Water. Bitter Hydrocyanic Glucose. 



bitter almonds. almond oil. acid. 



If after this the infusion of bitter almonds be distilled with water, the hydrocyanic acid 

 and the volatile bitter almond oil are carried over with the aqueous vapour. The latter 

 is insoluble in water, or only sparingly soluble, while the hydrocyanic acid remains as an 

 aqueous solution. Bitter almond water is similar to laurel water, and is used, like the 

 former, in medicine, naturally only in small quantities, because a considerable amount 

 lias poisonous effects. Perfectly pure anhydrous hydrocyanic acid keeps without change, 

 just like the weak solutions, but the strong solutions only keep in the presence of other 

 acids; but in the presence of many admixtures these solutions easily give a brown 

 polymeric substance, which is also formed from a solution of potassium cyanide. 



46 This salt will be described under potassium, as it is one of those which are often 

 used. 



D D 2 



