54 Mr. T. J. Pearsall on the 



Solutions of green chamelion and binoxalate of potassa were 

 heated in a retort ; the fluid soon became colourless, but with- 

 out changing the dilute solution of sulphate of indigo into 

 which the neck of the retort was introduced : the colourless 

 fluid was incapable of affecting indigo. 



Manganesic acid, mixed with oxalic acid, very powerfully 

 bleached indigb : neither oxalic acid nor the binoxalates have 

 any bleaching power over indigo, but manganesic acid and 

 some of its combinations possess this property. 



The colourless oxalate of potassa and manganese, which 

 remained in the retort after distillation, was rendered acid by 

 sulphuric and oxalic acids ; and then, upon the addition of 

 manganesic acid, a clear red solution was formed, which had 

 strong bleaching powers ; but it lost this property upon becom- 

 ing colourless, which it did in a short time. A very concen- 

 trated solution of red manganesate of potassa was added to 

 another portion of the same colourless triple oxalate ; the red 

 colour was more permanent, and the bleaching still more 

 energetic, than in the preceding experiments. These cases 

 afford experimental evidence that manganesic acid is capa- 

 ble of reproducing the characteristic properties of a crimson 

 solution supposed to contain a deutoxide. 



I shall now submit that the known properties of manganesic 

 acid and protoxide of manganese are capable of explaining the 

 action of acids upon the various oxides of this metal. The ex- 

 istence of either the red, deut, or peroxide in these fluids appears 

 to me to be an assumption : of course, the protoxide must 

 always be considered as present, according to the usual reason- 

 ing upon the relations of oxides to acids. The admitted action 

 of sulphuric acid upon peroxide is to form the protoxide, and 

 thus leaves the formation of the red solution by either the red 

 or the deutoxide quite unaccounted for; therefore it may 

 be advantageous to examine the changes which may be sup- 

 posed, in order to produce either of these oxides ; and, 1st, 

 it may be assumed, that the acid reduces the whole of the per- 

 oxide acted upon to the state of red oxide, or deutoxide which 

 forms a red solution ; or, 2dly, the acid reduces part of the per- 

 oxide to the state of protoxide, and another part to the state 

 of red or deutoxide, and both are in solution together ; or, 



