COMPOUNDS OF CARBON WITH OXYGEN AND NITROGEN 411 



Besides being a substance very prone to form polymerides, cyanic acid 

 presents many other features of interest, expounded in greater detail 

 in organic chemistry. However we may mention here the production 

 of the cyanates by the oxidation of the metallic cyanides. Potassium 

 cyanate, KCNO, is most often obtained in this way. Solutions of 

 oyanates by the addition, of sulphuric acid yield cyanic acid, which, 

 however, immediately decomposes : CNHO + H 2 C0 2 -f NH 3 . A 

 solution of ammonium cyanate, CN(NH 4 )0, behaves in the same 

 manner, but only in 'the cold. On being heated it completely changes 

 because it is transformed into urea. The composition of both sub- 

 stances is identical, CN 2 H 4 O, but the structure, or disposition of, and 

 connection between, the elements is different : in the ammonium 

 cyanate one atom of nitrogen exists in the form of cyanogen, CN" 

 that is, united with carbon and the other as ammonium, NH 4 , but, 

 as cyanic acid contains the hydroxyl radicle of carbonic acid, OH(CN), 

 the ammonium in this salt is united with oxygen. The composition of 

 this salt is best expressed by supposing one atom of the hydrogen in 

 water to be replaced by ammonium and the other by cyanogen i.e. 

 that its composition is not symmetrical whilst in urea both the 

 nitrogen atoms are symmetrically and uniformly disposed as regards 

 the radicle CO of carbonic acid : CO(NH 2 ) 2 . For this reason, urea is 

 much more stable than ammonium cyanate, and therefore the latter, 

 on being slightly heated in solution, is converted into urea. This 

 remarkable isomeric transformation was discovered by Wohler in 

 1828. 41 Formamide, HCONH 2 , and hydrocycmic acid, HCN, as a 

 nitrile, correspond with formic acid, HCOOH, and therefore ammonium 

 formate, HCOONH 4 , and formamide, when acted oh by heat and by 

 substances which take up water (phosphoric anhydride)form hydrocyanic 

 acid, HCN, whilst, under many conditions (for instance, on combining 

 with hydrochloric acid in presence of water), this hydrocyanic acid forms 

 formic acid and ammonia. Although containing hydrogen in the 

 presence of two acid-forming elements namely, carbon and nitrogen 42 



41 It lias an important historical interest, more especially as at that time such 'an 

 easy preparation of substances occurring in organisms without the aid of organic life was 

 quite unexpected, for they were supposed to be formed under the influence of the forces 

 acting in organisms, and without the latter their formation was" considered impossible. 

 And in addition to destroying this illusion, the easy transition of NH 4 OCN into CO(NH 2 ) 2 

 is the best example of the passage of one system of equilibrium of atoms into another, 

 more stable system. 



42 If ammonia and methane (marsh gas) do not show any acid properties, that is in all 

 probability due to the presence of a large amount of hydrogen in both ; but in hydro- 

 cyanic acid one atom of hydrogen is under the influence of two acid-forming elements. 

 Acetylene, C 2 H2, which contains but little hydrogen, presents acid properties in certain 

 respects, for its hydrogen is easily replaced by metals. Hydrouitrous acid, HN 3 , 

 which contains little hydrogen, also has the properties of an acid. 



