64 ESSAY V. 



necessary for its solution, by means of concentrated vitriolic 

 acid, from heat. It is not probable that the concentrated 

 acid undergoes a decomposition in this degree of fire ; for if 

 you saturate half an ounce of this acid with alkali of tartar, 

 and afterwards calcine in a retort, with a receiver applied, 

 li oz. of powdered manganese, with an equal quantity of the 

 same vitriolic acid, then dissolve the calcined mass in distilled 

 water, and likewise wash well the receiver, which contains 

 some drops of vitriolic acid, which are also to be added to the 

 solution, and lastly, add the same quantity of alkali, there 

 will be no mark either of abundant alkali or acid. Thence 

 it may be concluded that the phlogiston in the vitriolic acid 

 (if there really exists any in it) contributes nothing to the 

 solution. But the manganese, precipitated with alkali, 

 contains a considerable quantity of it ; in consequence of 

 which it is afterwards entirely soluble in acids, without the 

 addition of any phlogiston. 



SECTION XVIII. 



Manganese is often mixed with heterogeneous earths, 

 which are not to be reckoned as its constituent parts. 

 Among these are (1) a little iron ochre. This was the reason 

 why the mass in the retort, after distillation, was red on the 

 outside (Sec. u. (c)), because it was there exposed to the 

 greatest heat ; whence the vitriolic acid that was combined 

 with the iron, quitted it. Calx of iron is besides easily 

 obtained from the solutions of manganese in acids. If a few 

 drops of a solution of alkali are dropped in, the iron will be 

 precipitated first, because it has less attraction for the acid 

 than the phlogisticated manganese has. That this small 

 quantity of calx of iron is only mechanically mixed with 

 manganese, has been proved by Mr. Pott, and afterwards by 



