§ 53. MANGANESE. 71 



above ; the solution should contain no free chlorine or ni- 

 tric acid. 



The standard solution of hyposulphite should be care- 

 fully protected from the light, and the determination of 

 its strength should be repeated from time to time by com- 

 parison with a portion of the solution of ferric chloride 

 of known strength, as above. 



MANGANESE. Mn. 55. 



53. Compounds of manganese with phosphoric, car- 

 bonic, oxalic, and silicic acids, and sulphur, fluorine, and 

 cyanogen, are insoluble or sparingly soluble in water. 

 The silicate is insoluble in acids. 



Reactions* — A solution containing manganese gives a 

 precipitate, MnO,H20, or MnH^O^, with sodic or amnionic 

 hydrate ; the presence of amraonic chloride prevents the 

 formation of the precipitate by ammonic hydrate ; in this 

 way manganese may be partially separated from iron for 

 qualitative purposes. 



When a compound of manganese is fused with potassic 

 and sodic carbonate and sodic nitrate, the fused mass 

 takes a bluish-green color, which can be masked only by 

 the presence of a very considerable quantity of iron. In 

 case this large proportion of iron is present, it may be 

 precipitated by ammonia after adding considerable am- 

 monic chloride, filtering it out quickly, and evaporating 

 the filtrate ; then test a few drops of the concentrated 

 liquid by fusion, as above. 



Quantitatiyc estimation. — The manganese is usually 

 precipitated as carbonate ; when ignited, this carbonate is 

 converted into manganous manganic oxide, MugO^, which 

 is weighed. Heat the solution, free from any great excess 

 of mineral acid, nearly to boiling in a capacious flask, add 

 sodic carbonate very slowly until it is in excess, boil a few 

 minutes, and wash the precipitate by decantation and on 



