VALUATION OF MANGANESE ORES. 249 



combination with the protoxide of manganese, is 

 evolved in the form of carbonic acid. 



Fig. 34. 



One equiv. of pure binoxide of manganese = 43.6, 

 yields 2 equivs. = 44 of carbonic acid. So that 0.99 

 grm. of binoxide of manganese evolves 1.00 grm. of 

 carbonic acid. It is best to employ three times, that 

 quantity of the manganese ore, viz : 2.97 grms., which 

 are mixed with a solution of 2.5 grms. of neutral 

 oxalate of potassa ; the sulphuric acid is allowed to 

 flow into this mixture, and the amount of carbonic 

 acid evolved is divided by 3. The quotient expresses 

 the percentage of binoxide of manganese contained in 

 the ore. 



II. The finely-divided manganese ore is weighed, 

 and mixed with water, in a flask capable of being 

 tightly closed ; several bright strips of copper, previ- 

 ously weighed, are then introduced, and a quantity of 

 hydrochloric acid added. The flask is then closed 

 with a cork and narrow tube, and the contents digested 

 until all the manganese has dissolved, care being taken 

 that no chlorine is evolved. The liquid is then heated 



