ON MANGANESE 61 



over in the form of blood-red vapours, and yield green 

 volatile nitrous acid. In the retort there will remain like- 

 wise real black manganese, (c) A solution of manganese in 

 vitriolic or pure nitrous acid (Sees. n. (b), iv. (a)), precipitated 

 by alkali of tartar, retains its colour ; but when calcined 

 in the open air, grows black (Sec. xiv. (4)). Hence it 

 follows that manganese contains phlogiston ; and since the 

 residuums in the retort have lost their phlogiston, by means 

 of which they were united with the acids, they were no 

 longer soluble in pure acids. If, therefore, vitriolic acid be 

 poured upon the residuum (a), little or nothing of it will be 

 dissolved ; but if the volatile vitriolic acid which was driven 

 over into the receiver be poured upon it, it will again 

 dissolve it, a small portion excepted, for want of a sufficient 

 quantity of acid ; for there is some of the acid lost during 

 the distillation through the lute. The same thing happens 

 with the distillation and solution of manganese in nitrous 

 acid (b). 



SECTION XVI. 



Now, since only a part of this mineral is dissolved by the 

 vitriolic acid, it may be asked, why the remainder does not 

 dissolve ? To this I answer : The undissolved portion has 

 parted with the little phlogiston it naturally possessed, to 

 that portion of manganese which is taken up by the vitriolic 

 acid during the first digestion ; for, without that principle, 

 manganese is insoluble. That the remaining manganese loses 

 its phlogiston is evident from this, that if nitrous acid be 

 abstracted from it, there appears little or no red vapour. 

 That manganese, according to its second general property, 

 attracts phlogiston more strongly when it is combined with 

 some acid, the following experiments will show: (a) Levigated 

 manganese digested or boiled with a solution of sugar, honey, 



