372 IRON, NICKEL, COBALT, &c. 



composition. Sulphuric acid disengages it from 

 the potash ; but when we endeavour to separate 

 the sulphate of potash by evaporation, the red 

 colour disappears, and tritoxide of manganese 

 precipitates. 



B u t Dr. Forchhammer succeeded by a very 



mer s mode 



of obtaining ingenious process in obtaining manganesic acid 



manganesic , . . , , 



acid. in a separate state, or at least combined merely 

 with water. He mixed together tritoxide of 

 manganese and crystallized nitrate of barytes, 

 and exposed the mixture to a heat just sufficient 

 to produce the fusion of the salt. Great care, he 

 says, must be taken not to drive oft' the water of 

 crystallization, otherwise the process does not 

 succeed.* The nitric acid is gradually decompos- 

 ed. The tritoxide of manganese unites with more 

 oxygen, is converted into an acid, and combines 

 with the barytes, as that alkali is disengaged. 

 After the process is finished, the mass must be 

 digested in water, which dissolves any pure ba- 

 rytes, or nitrate of barytes, that may be present; 

 but does not touch the compound of barytes and 

 acid of manganese, \vhich is insoluble in that 

 liquid. To this insoluble residuum Dr. Forch- 

 liammer added the quantity of sulphuric acid 

 just capable of saturating all the barytes which 

 it contained. The acid of manganese in the 



* I have not attempted to repeat this process, because I have never met 

 \vith any nitrate of barytes that contained any water of crystallization. As 

 far as my observations go, the salt is always anhydrous. 



