HYDROMELONIC ACID. 67 



In preparing sulpho-cyanic acid, when the mixture of prussiate 

 of potash and sulphur had been heated too high, he occasionally 

 got small quantities of another salt. In such cases, when the 

 iron had been precipitated, and the filtered liquid, after having 

 been sufficiently concentrated, was set aside, white cauliflower- 

 looking crystals of this new salt were deposited. These being 

 again dissolved in hot water, crystallized, exposed to pressure, 

 and washed with hot alcohol till the salt no longer struck a red 

 with the persalts of iron, were considered as freed from all ad- 

 mixture of sulpho-cyanate of potash. When this salt was dis- 

 solved in boiling water, and the solution mixed with muriatic, 

 sulphuric, or nitric acid, a dirty-white gelatinous precipitate fell, 

 which dried into a yellow powder. This precipitate is a hydrate 

 of hydromelonic acid. It is slightly soluble in cold water, but 

 more soluble in that liquid when hot. It dissolves also in alco- 

 hol. It is destitute of taste and smell, but has a feeble acid re- 

 action. When heated it decrepitates slightly, and leaves melon, 

 which may also be driven off by continuing the heat. It dis- 

 solves readily in nitric acid, and the solution may be evaporated 

 without decomposing the hydromelonic acid. It dissolves also 

 in sulphuric acid. Hydromelonate of po ash effervesces when 

 heated with nitric acid, dissolves in water, and is decomposed by 

 acids. 



To analyze this acid, Grmelin employed hydromelonate of lead, 

 dried in the open air at 60. 100 parts of this salt exposed to a 

 heat of 212, lost 11 '08 7 parts of water ; and when the heat was 

 raised to 248, it suffered an additional loss of 3-043 ; making 

 the whole water in the salt amount to 14*13 per cent. 100 parts 

 of the same salt being decomposed by sulphuric acid, left 6 2 '3 8 

 of sulphate of lead, equivalent to 45^946 of oxide of lead. Hence 

 the constituents of the salt were 



Hydromelonic acid, . 39*906 or 12-154 = 1 atom. 



Oxide of lead, . . 45*964 or 14 1 atom. 



Water, - . . 14*130 or 3*304 = 4 atoms. 



100-000 



This analysis gives as the atomic weight of hydromelonic acid, 

 12*154. 



Gmelm analyzed hydrous hydromelonate of lead by means of 

 oxide of copper, and obtained 



