66 ESSAY V. 



SECTION XX. 



The effects of volatile sulphureous acid on manganese 

 clearly prove what has been asserted (Sec. m.). The 

 manganese attracts the phlogiston contained in this acid, 

 which is the cause of its great volatility, and which renders 

 the manganese soluble in the now pure vitriolic acid. If 

 this solution be mixed with concentrated vitriolic acid and 

 distilled, no volatile sulphureous acid is obtained ; and if it 

 be precipitated by means of fixed vegetable alkali, vitriolated 

 tartar is obtained. This proves that manganese has a 

 stronger attraction for phlogiston than for vitriolic acid 

 in the moist way. 



SECTION XXI. 



The effects of nitrous acid on manganese coincide, upon 

 the whole, with those of vitriolic acid. If this acid could 

 support such a degree of heat as the other in a state of 

 concentration, it would also entirely dissolve the manganese 

 without the addition of any phlogiston. But as this is not 

 the case, it is necessary to supply the defect of phlogiston. 

 The extraneous substances mixed with it appear in this 

 process more clearly, Sec. xvin. Here the pure siliceous 

 earth remains undissolved at the bottom; but another 

 unknown earth unites with the nitrous acid, and yields 

 crystals, Sec. iv. (c). It likewise may be precipitated by 

 the vitriolic acid ; and this is the precipitate mentioned in 

 the same place (&) as insoluble in water. The calcareous 

 earth, with vitriolic acid, forms gypsum, and the small 

 portion of iron is readily separated by means of a few 

 drops of alkali of tartar (Sec. xvin. (1)). 



