Vpon th Preparatlbfi'^df'plTe Bar?/feL '^l 



much concentrated that no barytcs remains hi solutian ; that 

 whatever precaution we may take in the preparation of the 

 '«anstic alkah by Hme, if not during the fihrations, there will 

 alwavs be a portion of it carbonated; consequently, the t^ame 

 quantity will be w:inting in the quantity of baryte^j we ouglit 

 to obtain: that, besides this, during its precipitation, as we 

 are obliged to shake the liquor, it carbonates a certain (|uah- 

 tity of it: that by washing also we experience a feal loss,; 

 and lastly, that by a hew soiutit)n in boiling water it carbo- 

 nates still more of it ; ' it is visible that all these subtrac- 

 tions united leave but a small quantity, while by the de- 

 composition of the nitrate we absolutely obtain 'tfate %hoTb 

 quantity of barytes it contains, and which amoiints to very 

 near the half of the weight of dry salt j and that besides, this 

 operation is neither difBcult nor expetisive, when we know 

 how to manage it properly. 



Nov/ the following arc the precautions necessary to ensure 

 success : 



Fill near two thirds of the crucible with dry and pulve- 

 rized nitrate ; place the crucible with its lid in a common 

 furnace, in a gentle heat, so as merely to melt the salt rn 

 Its water of crystallization; increase the fire progressively 

 and with caution, on account of the swelling up which 

 latterly takes place: when the mass, which should be then 

 of a cherry red/ lets no more bubbles escape, cover the cru- 

 cible with an inch or two of charcoal; adapt to the furnace 

 its dome provided with a pipe of gun metal : heat it thus for 

 a quarter of an hour; take the crucible from the fire; 'break 

 it, and pack up the barytes as quickly as possible. 



I also treated by this process seven pounds* 6f iiiiraie, 

 which I had divided into three common crucibles and placed 

 in one furnace : I produced the complete decomposition in 

 two hours, and T obtained three pounds six ounces of per- 

 fectly pure barytes. But it must be observed, that if the ba- 

 rytes is kept too long in the fire after the decomposition of 

 the nitrate, it is carbonated considerably, and it is afterwards 

 completely impossible, whatever heat we employ, to deprive 

 it entirely of carbonic acid. This is the whole difficulty at- 

 tending my operation. I am therefore of opinion that it is 

 p I really 



