60 ESSAY V. 



discovered by a train of experiments, all its known effects 

 are easily explicable, as will appear from the following 

 observations. 



SECTION XV. 



Diluted vitriolic acid dissolves manganese only in part, 

 whether digested or boiled with it (Sec. n. (a)). This part 

 therefore ought to be separated from the rest, because the 

 solution of manganese is never colourless, except when 

 combined with phlogiston (Sec. xiv. (4)). Whence it follows 

 that this soluble part of it is united with phlogiston. 

 That manganese naturally contains but little phlogiston, has 

 been some time ago taught by Mr. Westfeld ; but the cause 

 he assigns is not to be admitted till it is confirmed by other 

 arguments, especially as nitre, without the addition of 

 phlogiston, may become alkalescent, and that the sooner if 

 there be a body present which is capable of uniting with the 

 alkali, in which case a heat only half as strong is requisite. 

 This happens in the calcination of manganese with nitre ; 

 for if the mixture is distilled, nitrous acid is obtained in the 

 receiver ; but that some phlogiston really enters into the 

 composition of manganese, the following experiments will 

 show : (a) If the solution of manganese in vitriolic acid 

 (Sec. u. (a\ (&)) be evaporated to dryness, and then the 

 residuum distilled in the open fire in a glass retort, with a 

 receiver applied to it, the vitriolic acid does not separate from 

 the manganese till the retort begins to melt ; but it is then 

 changed into volatile sulphureous acid. The residuum is black, 

 and nothing but common manganese. (&) Let the solution of 

 manganese in nitrous acid (Sec. iv. (a)) be put into a glass 

 retort, all the liquid abstracted, and when it begins to foam, 

 let a receiver, with some water in it, be applied. By a slow 

 fire, the nitrous acid employed for the solution will be driven 



