1820.] Maiiganeseous and Manganesic Acids. 133 



holds also with the nitrate of potash. As there is, therefore, no 

 hope that in that way a tolerably pure manganesic acid may be 

 obtained, I shall not repeat the numerous experiments winch 1 

 tried in vain to get this acid pure, but only state the process by 



which I succeeded. ■ r i, j jj j 



I prepared a solution of submanganesite of potash, and added 

 to it a solution of nitrate of lead, which threw down a brown 

 powder, and destroyed the green colour entirely. This brown 

 powder was washed as long as it contained any soluble body. It 

 was then carefully mixed with sulphuric acid, diluted with 10 

 times its weight of water. It is necessary to preserve a portion 

 of the brown powder in order to be able to neutralize any excess 

 of sulphuric acid that may happen to have been added, A long 

 dio-estion of the liquid with the brown powder is necessary lu 

 order to combine all the sulphuric acid with the lead. We must 

 beware not to dry the brown powder as it is only in the state of 

 hydrate that it is capable of forming the manganesic acid. 



This process is easily explained. The protoxide of lead is by 

 the manganeseous acid changed into peroxide, which combining 

 with the deutoxide of manganese forms the brown powder. 

 When sulohuric acid is added, it causes thfe peroxide ot lead to 

 o-ive a part of its oxygen to the deutoxide of manganese, and 

 produces manganesic acid, deutoxide of manganese, and sul- 

 phate of lead. The manganesic acid thus obtained is of the 

 most beautiful red colour, is easily soluble in water, has a sharp 

 unpleasant taste, and stains the skin and other animal and vege- 

 table substances of a beautiful brown colour. It destroys the 

 colour of htmus paper, and renders it brown by depositing deut- 

 oxide of manganese, and it would bleach quite as well as 

 chlorine or oxidated water, if its oxide was not coloured itself, 

 and produced a new colour. 



When heated and evaporated, it is decomposed; it forms 

 brown oxide of manganese, and gives a smell almost like that 

 which the glass of an electrical machine gives when rubbed ; the 

 same smell rises, when the manganesic acid is exposed to the 

 beams of the sun. The nature of this vapour I was not able to 

 make out ; whether it was an oxide of manganese, or other 

 substance, I cannot say. When manganesic acid is heated with 

 muriatic acid it is entirely decomposed, and reduced to protox- 

 ide, which combines with the muriatic acid. As I was not in 

 possession of a good air-pump, I could not ascertain what effect 

 the concentration of the manganesic acid by means of sulphuric 

 acid in the vacuum would produce, and whether it would yield 

 crystals. Potash, or any other alkali, is not at all required for 

 the formation of the manganesic acid ; hydrated peroxide of 

 lead, sulphate of magnesia, and sulphuric acid, mixed together 

 will produce the same body ; but in this case, it is still more 

 difficult to get it free from sulphuric acid. In several analyses I 

 used the following way to separate salts of manganese and mag- 



