40 MR JOHNSTON ON PARACYANOGEN 



As this mode of analysis gives the water with great accuracy, we may de- 

 duct 1.13 from 4.22, and we have 3.09 of dry acid, containing 1.3466 of carbon 

 = 43.481 per cent. And as the C : N : : 2 : 1, we have for tlie constitution of the 

 dry acid, 



Calculation. Experiment 



Cs = 611.496 = 43.074 = 43.481 

 N4 = 708.144 = 49.882 = 50.035 

 0, = 100.000 = 7.044 = 6.484 



Atom. = 1419.640 100 100 



The quantity of carbon obtained is a little too high, which may be attributed 

 to the absorption by the caustic potash of a small quantity of binoxide, which 

 was recognised by the smell during the process. This excess of carbon neces- 

 sarily causes an excess also in the nitrogen calculated from it, and a correspond- 

 ing deficiency in the per-centage of oxygen. 



If the water in the acid be 5 atoms, we have 



Theory. Experiment. 



Carbon, . . . . = 30.85 = 31.91 

 Nitrogen and oxygen, = 40.78 = 41.303 

 Water, = 28.37 = 26.777 



100 100 



As the acid, however, was dried only at 212° Fahr., I do not place much con- 

 fidence in the fiumber of atoms of water. It should probably retain, when fully 

 dry, at this temperature, only four atoms of water, as the salt of silver appears 

 to do, in which case the formula for the hydrated acid would be Cg N4 4- 4 HO. 



8. Being insoluble in water, or nearly so, this acid does not afiect litmus. 

 In hot concentrated solutions of the caustic alkalies, it dissolves with partial de- 

 composition and evolution of ammonia ; in weaker solutions it is very sparingly 

 soluble, and very little also is taken up by solution of caustic ammonia. It has 

 a powerful afiinity, however, for certain metallic oxides, especially for those of 

 mercury and silver, with both of which it forms compounds very slightly acted 

 upon by water, and with difficulty decomposable even by the mineral acids. 



This acid, indeed, is remarkably distinguished from the cyanic (Cy 0), and 

 fulminic NCjO acids by its great stability. It is decomposed very slowly by hot 

 concentrated nitric and sulphuric acids, protracted boiling being necessary to pro- 

 duce complete decomposition. Its affinity for the oxide of mercury is so great, 

 that a weak solution of nitrate of mercury throws down the paracyanate from a 

 solution of the yellow acid in the nitric or sulphuric acid. 



