30 Dr. Turner's Chemical Examination 



of manganese. When it conies in contact with concentrated 

 sulphuric acid, an intense heat is instantly evolved ; and the 

 same phsenomenon is produced, though in a less degree, by 

 strong muriatic acid. This oxide is likewise the base of the 

 salts which are formed when sulphuric or muriatic acid is 

 heated with the peroxide, deutoxide, or red oxide of manga- 

 nese. As the accuracy of this statement, as respects sulphuric 

 acid, has been denied by an acute chemist and good observer, 

 I have been induced to examine the question with considera- 

 ble care. I mentioned in my Elements of Chemistry, in ex- 

 plaining the process for procuring oxygen gas by means of 

 sulphuric acid and the black oxide of manganese, that the 

 peroxide loses a whole proportion of oxygen, and is converted 

 into the protoxide, which unites with the acid, forming a sul- 

 phate of the protoxide of manganese. The gentleman who 

 has done me the honour to review that work in the Annals of 

 Philosophy, I apprehend Mr. Richard Phillips, has made the 

 following remark on the preceding passage. " This statement 

 is at variance with both Dr. Thomson's and also with the results 

 of our experiments ; for we find that 44 or one atom of peroxide 

 of manganese yield 4*2 of oxygen, which is so much nearer 4 

 than 8, that there is no question but that the deutoxide, and 

 not the protoxide is obtained by the action of sulphuric acid ; 

 that this is the case is further proved by the deep red colour 

 of the solution of the sulphate, and by its losing that colour, 

 as stated by Dr. Thomson, when mixed with sulphurous or 

 nitrous acid." 



To decide this point between the reviewer and myself, it is 

 only necessary to heat the peroxide of manganese with con- 

 centrated sulphuric acid, so as to form a solution highly charged 

 with the oxide of manganese, and decant off the solution while 

 hot from the undecomposed peroxide. The liquid on cooling 

 deposits a perfectly white salt, which possesses every property 

 of the protosulphate of manganese. If the acid, which retains 

 an amethyst-tint even when cold, be again heated, the red co-* 

 lour speedily disappears ; because the red oxide, which is dis- 

 solved in small quantity by the sulphuric acid, is then also 

 converted into the protoxide with the evolution of oxygen gas. 

 The red colour disappears gradually even without the aid of 

 heat ; for the solution will be found after a few days to be al- 

 most and sometimes quite colourless, while a minute quantity 

 of red oxide has subsided to the bottom. On applying a very 

 gentle heat, the red oxide is redissolved, and the acid acquires 

 a lively amethyst-red colour. It is easy, by operating in this 

 way, to obtain satisfactory proof, that a minute portion of red 

 oxide suffices to communicate a rich colour to a considerable 



quantity 



