ly the Oxides of Lead and of MaJ}gnr}ese. 73 



quantity of nitric acid which it requires. Barvtes will cer- 

 tainly become a very valuable substance for the arts, when 

 we shall be able to procure it at a reasonable price. 



The following is the most simple and the most cecono- 

 mical means which I have discovered, and which i had a 

 long time practised for my own use. 



When sulphuret of barytes is made by the decomposition 

 of sulphate of barytes and charcoal, I dissolve it in water j 

 after having let it settle and clear itself, I decant it into a 

 vessel, in which I boil it, adding to it pulverized oxide of 

 manganese, till the liquor has lost its yellow colour, and is 

 become clear and limpid. 



In proportion as the oxide of manganese separates the 

 sulphur from the barvtes, the odour of sulphur diminishes, 

 and instead of it an alkaline odour is perceived; the taste 

 of the liquor, when all the sulphur is combined with the 

 manganese, has a considerable degree of causticity ; as soon 

 as it cools, if too much watei- has not been employed for the 

 solution of the sulphuret, the barytos crystallizes round the 

 vessel. 



Nitrate of lead and sulphate of copper are precipitated 

 from their solvents by caustic barvtes, the first in a white, 

 and the second in a blue form : thus oxide of manganese 

 has a stronger aflinity with sulphur than either soda or 

 caustic barytes has, s;nce this oxide, at the mere degree of 

 ebullition, decon^poses these alkaline sulphiiretscompletely- 

 This process appeared to me simple enough to be applied 

 to the preparation of these two alkalies upon a large scale, 

 so as to aflord them at a reasonable expense to the arts in 

 which they may be used. 



Since I first perceived that oxide of manganese attracted, 

 in the humid wav, sulphur from fixed alkalies and from 

 barytes, this means has been a great assistance to me in 

 getting rid of the alkaline sulphurets in many analytical 

 operations, in which the presence of the alkaline sulphuret 

 embarrassed me, without my requiring an acid to decom- 

 pose it. 



Soda and barytes prepared by this process are very pure, 

 and are obtained at a very moderate expense, especially 

 barytes. 



XV. Pro- 



