1 80 M. JE, Mitscherlich on 



position. If the solution be allowed to evaporate in contact 

 with the atmosphere, red crystals, the composition of which, 

 I shall attend to afterwards, may be formed by the action 

 of the carbonic acid of the air. 



If the green crystals be treated with water, a red solution 

 is obtained, which, by evaporation, yields red crystals. The 

 green crystals consist of manganate of potash, which is 

 isomorphous with sulphate of potash, while the red have 

 the same form as the perchlorate of potash. Accurate 

 analyses have shown that both the perchloric acid and the 

 highest degree of oxidation of manganese, contain 7 propor- 

 tions of oxygen. It appears to me, therefore, to be conve- 

 nient to denominate that degree of oxidation of manganese 

 which corresponds with sulphuric, selenic, and chromic 

 acids, manganic acid, while the highest degree of oxidation 

 of manganese may be called hypermanganic acid, and that 

 of chlorine hyperchloric acid, following the nomenclature of 

 Gay Lussac with respect to %/>o-sulphuric acid.* 



II. — Manganic Acid and its Salts. 



I had tried many ways of analyzing manganic and hyper- 

 manganic acids, when at last, I met with one as accurate as 

 it was easy. It depends on the fact, that hypermanganic 

 acid begins to decompose at the temperature of 86° F., and 

 at 212° is completely changed into binoxide and oxygen gas, 

 and as the manganate of potash when treated with water 

 changes into hypermanganate of potash and binoxide of 

 manganese, the compounds of manganic acid may be ana- 

 lyzed the same way. I add to the manganic or hyper-man- 

 ganic acid, sulphuric or nitric acid, collect the oxygen in a 

 graduated tube over quick-silver, and reduce the gas obtained 

 to what it would be at 32° F. and when the barometer 

 stands at 30 inches. 



0*705 gramme of manganate of potash, treated with 

 dilute nitric acid, and boiled till the solution became 

 colourless, gave 58*9 cubic centimetres dry oxygen gas, 

 which is equivalent to 0*0844 gr. by weight. 100 parts of 

 the salt had, therefore, given out 8*7 of oxygen when treated 

 with nitric acid. 



• In this investigation I have been greatly aided in the preparation of tlie sub- 

 stances by my assistant, M. WolfF, a very skilful pharmaceutist. 



