32l2 MAONESIAN EARTtf. 



There remains jet for me to examine the economical ufes 

 for which this earth may be employed. 



The experiment which I related in the beginning of this 

 memoir, of the decomposition of the fulphate of iron by this 

 earth, wiiich produced an excellent fulphate ©f magnefia, in- 

 dicates one of the methods in which it might be ufed to ad- 

 vantage. 

 Sulphate of mag-.. Twenty-five pounds of fulphate of iron coft only three francs 

 nefia may be ^j, u <. w h\\e the price of the fame weight of fulphate of 

 manufactured r . . . r r . r- n i • 



from it to ad- magnefia is eight franc?, from this it follows that this procels 



vantage by the may De followed to advantage. To this may be added that 

 fulphate of iron, tne fulphate of magnefia of commerce, being impure, and 

 defcribed before, mixed with much fulphate of foda, cannot be compared to that 

 thaTof com- *" wrucn mav De procured in this manner, which equals the bed 

 merce in general, fait from * * canal; fo that in this comparifon the more pure 

 fulphate of magnefia thus obtained, may be valued at ten francs 

 at leaft, and in reality is worth more. 



This however is not the belt method to purfue, wherr the 

 operator has it in his power to follow the others, which I am 

 going to recite. 



The following experiments make known two procefles much 

 more economical. 



In the firft experiment I took two pounds of the earth of 

 Baudiflero, reduced to a coarfe powder, with the fame quan-r 

 tity of the fulphuret of iron of Brozo reduced to powder in 

 like manner, I mixed them together carefully, and treated one 

 half in a crucible on the Cue, and the other half in an iron 

 capfule. 

 Or by pounding In both the mixture heated to rednefs emitted fparks, efpe- 

 thefe and heat- cially on being ftirred. It feemed to become reduced to a 

 crucibles; vcrv ^ ne powder; a fort of boiling took place, produced 



doubtlefsly by the difengagement of carbonic acid, and here 

 and there appeared flames of fulpbur, which burned without 

 exhibiting any fign of the production or' a fulphuret. The 

 fulphurous odour was not however very troublefome, from 

 whence it appeared that the magnefia abforbed with readinefs 

 the. fulphuric and fulphurous acids in proportion as they 

 were formed by combuftion. The mixture became of a black- 

 ifh 'zrey, or more properly a black; but which appeared grey 

 frfun the white particles which flill remained mixed with it. 



After 



