CYANOGEN. 



cbvioufly compofed of two atoms or volumes of carbon, and 

 one atom or volume of azote, or per cent, of 



Carbon ... 70.0 



Azote ... 30.0 



1 00.0 



See Atomic Theory, Table III. 



Cyanogen is capable of combining with chlorine, and 

 forming an acid which has been named chlorocyanic acid. It 

 alfo combines with hydrogen, forming hydrocyanic acid ; with 

 fulphur, forming fulphocyan'tc acid ; and with iron, forming 

 ferrocyank acid: of each of which acids we fliall here give a 

 brief account. 



Chlorocyanic Acid. — This is the oxypnijfic acid of Ber- 

 thollet, who firft demonftrated its exiftence. Its properties 

 were afterwards more thoroughly inveftigated, and its true 

 compofition pointed out by M. Gay LulTac, who gave it the 

 above name. The acid was formed by M. Gay Luflac by 

 pafling a current of chlorine gas through a folution of hydro- 

 \ cyanic acid (pruffic acid, fee below) in water, till the liquid 

 difcoloured indigo diffolved in fulphuric acid. To feparate 

 the excefs of chlorine, the mixture was agitated with mer- 

 cury. The chlorocyanic acid was fubfequently feparated 

 by an ingenious procefs. A glafs cylinder, filled two-thirds 

 "with mercury, was filled to the brim with the above mixture, 

 and then inverted into a bafin of mercury. The appa- 

 ratus was put under the receiver of an air-pump, and the 

 exhauftion carried on till the whole of the mercury and 

 liquid was difplaced, and the cylinder filled with chlorocyanic 

 acid in a ftate of vapour. On letting the air again into the 

 receiver the vapour was condenfed into a liquid, and thus col- 

 iefted upon the furface of the mercury in the cylinder. 

 Chlorocyanic acid thus obtained is a colourlefs liquid, having 

 a ftrong and peculiar odour, which excites fuch irritation as 

 to induce a flow of tears. It reddens litmus, is not inflam- 

 mable, and does not detonate when mixed with hydrogen or 

 oxygen. Its folution in water does not precipitate nitrate 

 of filver, nor barytes water. The alkalies abforb it rapidly, 

 tut it requires an excefs of them to deilroy its odour com- 

 - pletely. It throws down iron from its folution of a green 

 colour. But fome of its compounds appear of a very per- 

 manent nature. Gay Luffac has (hewn that this acid is 

 a compound of one atom or volume of cyanogen, and one 

 •atom or volume of chlorine, united together without change 

 of bulk. Hence it will be compofed ^fr cent, of 



Cyanogen 

 Chlorine 



41-93 

 58.07 



And its fpecific gravity in a ftate of vapour will be 2.152. 



Hydrocyanic Acid. — This was formerly denominated 

 Prussic Acid ; which fee. Hydrocyanic acid may be pre- 

 pared in the manner pointed out in the above article ; but the 

 method more lately recommended by Gay Luffac confifls 

 in decompofing the pruffiate of mercury by means of muriatic 

 acid in a retort with heat. The produfts are to be paffed 

 through a tube two feet long, the firft one-third of whofe 

 length is to be filled with fragments of marble, to retain the 

 muriatic acid that may come over, and the remaining two- 

 thirds with dry muriate of lime. A fmall receiver covered 

 with ice is to be adapted to the end of this tube in which 

 the hydrocyanic acid may be coUefted on application of 

 .a moderate heat to the retort. The properties of this acid 

 are correftly defcribed under Prussic Acid. It is a moft 



Vol. XXXIX. 



virulent poifon. From Gay Luffac's experiments, it appears 

 to be compofed of one atom or volume of cyanogen, and one 

 atom or volume of hydrogen, united together without 

 condenfation. Hence it is compofed ^i'r cent, of 

 Cyanogen - - - 56. j 



Hydrogen - - - ^.-j 



And the fpecific gravity of its vapour will be .9367. 



Hydrocyanic acid cannot be preferved for any length of 

 time without undergoing decompofition, ammonia is formed, 

 and a quantity of charry matter is depofited. Iodine vola- 

 tilized in this acid fuffers no change. Oxygen decompofing 

 It with combuftion. Chlorine difplaces the hydrogen, and 

 forms chlorocyanic acid. Neither azote, hydrogen, carbon, 

 boron, filica, nor phofphorus, have any known aftion upon it. 

 Sulphur decompofes it, appearing to difplace the hydrogen 

 andcombine with thecyanogen, and thus forming fulphocyanic 

 acid. PotalTium, fodium, potafti, foda, and barytes, combine 

 with the cyanogen and liberate the hydrogen. The vapour 

 of hydrocyanic acid is decompofed when paffed through red-- 

 hot iron or platina ; alfo when paffed through the peroxyd 

 of copper. The peroxyd of manganefe completely abforbs 

 the vapour of hydrocyanic acid in a few hours, water is 

 formed, but cyanogen is not evolved. When the red oxyd of 

 mercury is heated in hydrocyanic acid vapour, fo much heat 

 is evolved from the violent aftion that takes place that the 

 compound is deftroyed. If heat be not apphed, the vapour 

 is abforbed by the oxyd, and when the compound is after- 

 wards fubmittcd to heat, water is difengaged, and the 

 cyanide, or pruffiate of mercury, as it was formerly termed, 

 is left behind. See further under Prussic Acid. 



SuJphocyanic Acid. — This is the ftilphuretted chyazic zc\Aoi 

 Mr. Porrett, who difcoveredit in 1808. It may be formed 

 by diffolving one part of fulphuret of potafh in water, and 

 boiling in this folution three or four parts of pruffian blue, 

 added at intervals. Sulphuret of iron is formed, and a 

 colourlefs neutral liquid containing a confiderable quantity 

 of fulphocyanic acid combined with potafli. This liquid 

 is then to be rendered decidedly acid by fulphuric acid, 

 and the mixture kept at the boiling point for fome time. 

 When cold, a little peroxyd of manganefe is to be added, 

 which will give to the folution a fine crimfon colour. This 

 crimfon liquid is to be filtered, and a folution compofed of 

 two parts of the perfulphate of copper and three of the 

 protofulphate of iron is to be added, till the crimfon colour 

 difappears. A copious white precipitate, compofed of 

 fulphocyanic acid and protoxyd of copper, takes place. 

 The copper may be feparated by boiling with a folution of ■ 

 potafh, and the fulphocyanate of potafli thus formed after- 

 wards decompofed by fulphuric acid ; the fulphocyanic acid 

 may be then obtained by diftillation in a retort. If any ful- 

 phuric acid adheres to it, this is to be feparated by a little 

 carbonate of barytes. 



Sulphocyanic acid thus formed is a tranfparent colour- 

 lefs liquid, having an odour as ftrong, and fomewhat refem- 

 bling acetic acid. Its fpecific gravity when moft concen- 

 trated was 1.022. According to Mr. Porrett's aiialyfis, it 

 is compofed of 



Sulphur - - - 65.2 

 Hydrocyanic acid - 34-^ 



1 00.0 



Dr. Thomfon feems inchned to confider this acid as com- 

 3 M poled 



