214' Mr. Phillips on a new Oxide of Manganese; SfC. 



There are some other statements in Dr. Turner's memoir, 

 on which I shall offer a few observations. He appears to doubt 

 the existence of a permanent red sulphate of manganese, and 

 to suppose, when it is obtained, that it soon becomes co- 

 lourless, a precipitate being deposited in it which is the red 

 oxide. " If the (sulphuric) acid," he observes, " which re- 

 tains an amethyst tint even when cold, be again heated, the 

 red colour speedily disappears ; because the red oxide, which 

 is dissolved 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 almost and sometimes quite colourless, when a minute 

 quantity of red oxide has subsided to the bottom. On apply- 

 ing 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 mi- 

 nute portion of red oxide suffices to communicate a rich co- 

 lour to a considerable quantity of sulphuric acid. The acid 

 may be made to retain the red colour, either by diluting it 

 with water, or by keeping it in contact with undissolved 

 oxide." 



I have frequently obtained the red sulphate of manganese, 

 possessing, not merely an amethyst tint, but a most intense 

 and beautiful red ; and I have kept such a solution for several 

 months without its depositing any oxide, and without keeping 

 it in contact with undissolved oxide ; and dilution with water 

 is so far from preserving the colour of the solution, that it is 

 instantly decomposed by it, and oxide of manganese depo- 

 sited. 



I have examined the circumstances under which this red 

 sulphate is produced ; and I shall take this opportunity of 

 stating the method by which it may be formed with certainty 

 and very readily. 



Before, however, I proceed to this part of the subject, I 

 will state the experiment upon which I have admitted that 

 when peroxide of manganese is dissolved by sulphuric acid, it 

 is converted into protoxide. For this purpose I used cry- 

 stallized native peroxide, which contained 1*2 per cent of si- 

 lica, and 0*6 of sulphuret of copper; of this 150 grains re- 

 duced to powder were heated in 2000 grains of sulphuric acid, 

 in the mode already described when treating of the War- 

 wickshire oxide. Without entering into minutiae;, I shall 

 merely state, that the 147*3 grains of pure peroxide which 

 the ore contains yielded 80 cubic inches of oxygen gas, con- 

 sequently 44 would have given 8-09 grains nearly; a quantity 



so 



