i-o ANALYSIS OF LITHOMARGE. 



cligeftcd in a folution of aerated alkali, pure ar- 

 gillaceous earth is obtained ; and which, in the 

 cafe before us, being waflied and dried, weigh- 

 ed 10.5 ; therefore equal to 21 Ib. in a hundred 

 weight. 



This method of determining the quantity of 

 argillaceous earth, is equally accurate and con- 

 venient. And, when a hundred weight of pure 

 cryilaline alum, diilblved in lixteen time* it> 

 weight of dillilled water, and deprived, in a tem- 

 perature of 90 degrees, of the excefs of acid, by 

 means of aerated magncfia, depofits 36 Ib. of 

 argillaceous earth cxadlly faturatcd with the vi- 

 triolic acid, by calling the given weight of 

 the precipitate a, the quantity of the earth will 



18. ico a a 

 be found s= = . After the point of 



36.100 2 



faturation is attained, the folution mufl be eva- 

 porated to a third of its bulk before the ledi- 

 mont is collected on the filrre. The precipita- 

 tion may be cfiecled like wife by fmali phtes of 

 v.inc, extended very thin under the hammer. 

 The folution of alum, though ilowly evaporat- 

 ed, depofits no fcdimcnt until reduced to near- 

 ly an eighth part; but if the water carried of}' in 



vapour 



vitriolatcd magnefu without any admixture of alum, aiul a 

 fmUl quantity only of gypfuin that had remained undifiolvcd 

 ;n the water of the folution. If the experiment is properly 

 inilitutcd in this manner, he will not be in the Icait influenced 

 by any opinions that may be advanced to the contrary. 



