Chemical Science, 177 



colour is changed to green, it is in consequence of the presence 

 of some body absorbing oxygen, as alcohol, prot-oxide of manga- 

 nese, 8fC. ; and Chevreul has shewn that even filtering through 

 paper will have the same effect. 



In attempts to get the manganesic acid pure, a solution of the 

 manganesiate of potash was prepared by passing carbonic acid 

 through the green solution, and when filtered, sulphuric acid 

 was added to it ; this spontaneously evaporated, gave crystals of 

 sulphate, manganesiate, and bi-sulphate of potash. As in this 

 experiment it was evident that if sulphuric acid at all decom- 

 posed the manganesiate, it only did so to form bi-sujphate of 

 potash ; it proved that no pure manganese acid could be ob- 

 tained in this manner. A solution of sub-manganesite of potash 

 was then prepared, and nitrate of lead in solution added to it, 

 which threw down a brown powder, and instantly destroyed the 

 green colour. This brown powder was washed, and then care- 

 fully mixed with sulphuric acid, diluted with ten times its 

 weight of water, a portion of the brown powjder bejng preserved 

 to neutralize any excess of acid on the powder. The powder 

 must not be dried before the acid be added to it, and long di- 

 gestion is necessary for the complete combination of the acid 

 and the lead. In this process the prot-oxide of lead is changed 

 into per-oxide by the manganeseous acid, which itself becomes 

 deut-oxide ; and the two combine, forming the brown powder. 

 On adding sulphuric acid the per-oxide of lead is decomposed 

 to form sulphate of lead, and its oxygen combining with part of 

 the deut-oxide of manganese coayevts it into manganesic acid ; 

 this is obtained by decantation, in a separate state. 



The manganesic acid thus obtained is in solution 1 ; it is of a 

 beautiful red colour, and sharp unpleasant taste ; it stains the 

 skin and other animal and vegetable substances of a fine brown 

 colour; it destroys the colour of litmus paper rendering it 

 brown by depositing deut-oxide, and would bleach well but that 

 the oxide deposited is of a brown colour itself. When evapo- 

 rated and heated it decomposes, forming brown oxide of manga- 

 nese, and giving a siyiell like that of an excited electrical 

 machine, and the same smell is produced from it by exposure 



Vol. X. N 



