Chemical Science* 491 



When decomposed by heat and oxide of copper, it yields azote 

 and carbonic acid j the proportions of these gases in volume being 

 1 and 15. These are exactly the same proportions which, accord- 

 ing to Mr. Crum, and also Dr. Buff, .are given by indigo itself j so 

 that the azote and carbon are in the same relation both in indigo 

 and the acid of indigo. The elements of the acid, according to 

 three experiments, are as follows: — 



Hydrogen 1.73 2.03 2.417 



Carbon 46.34 48.21 46.244 



Azote 7.22 7.55 7.225 



Oxygen 44.71 42.21 ......44.144 



The acid of indigo combines with all bases, and has power to 

 expel carbonic acid from carbonates. The salts have a yellow 

 colour. When heated, they are decomposed without explosion. 

 The proportional number of the acid drawn from its combination 

 with baryta is 254.7. ; for 100 parts of the acid combine with 30.07 

 of baryta. — Annales de Cliimie, xxxvii. 160. 



29. Artificial formation of Urea, by M. Wtihler. — Some time 

 since M. Wohler stated that when cyanogen acted upon liquid am-i 

 monia, amongst other products were oxalic acid and a white crys- 

 talline substance j the latter appeared to be formed also whenever 

 cyanic acid was combined with ammonia by double decomposition : 

 it is obtained most readily when cyanate of silver is decomposed 

 by muriate of ammonia, or cyanate of lead by pure ammonia : in 

 the latter way a quantity was prepared for experiment, and ap- 

 peared as colourless, transparent, four-sided rectangular crystals. 

 Nothing but oxide of lead and the particular substance is formed 

 in this process. 



Potash or lime evolve no ammonia from this substance, al- 

 though, supposing it a cyanate of ammonia, that might have been 

 expected -, and it is unlike the cyanates in that it does not evolve 

 carbonic and cyanic acids by the action of other acids, nor does 

 it precipitate salts of lead and silver, which would seem to imply 

 that it does not contain either ammonia or cyanic acid. 



When nitric acid is added to it, brilliant scaly crystals were 

 formed, which, when purified by crystallization, were very acid j 

 these being neutralized gave nothing but nitrates and the peculiar 

 matter in the state it originally possessed. This peculiar action 

 with nitric acid, induced a comparison of it with urea obtained 

 from urine, when the latter body was found to be identical with 

 the peculiar crystalline substance or cyanate of ammonia, in all 

 the properties attributed to the former body by Proust, Prout, 

 and others. M. Wohler remarks a circumstance, in addition to 

 those which have been pointed out relative to urea, namely, that 

 when either it or the artificial compound is decomposed by heat, 

 besides a large quantity of carbonate of ammonia, there is pro- 

 duced, towards the end of the operation, the odour of cyanic acid, 



