110 Analysis of Limestone, 



ly about one sixth) separated spontaneously, fell down 

 and was added to the first portion. 



The whole of the magnesia was then thrown down 

 by carbonat of potash, well washed, dried over a char- 

 eoal fire in the heat of about 160° and then weighed. 



The sulphat of lime, or gypsum, was exposed in a 

 crucible for two hours to a red heat, and the lime cal- 

 culated on the proportion of 100 parts limestone to 130 

 of the anhydrous gypsum. A proportion, for which I 

 will assign my reasons in a supplement to the present 

 paper. 



Secondly. I proceeded in another way. 



I treated the finely powdered limestone with strong 

 sulphuric acid (oil of vitriol of commerce;) triturating 

 them together in a glass mortar. 1 then added four 

 times the quantity of water. The clear liquor was de- 

 canted from the sediment which w^as washed with an« 

 other portion of water, and the liquors added together. 

 The sediment (gypsum) was rendered anhydrous by 

 exposure to a red heat in a crucible for two hours, and 

 the limestone calculated on the proportion of 10 parts 

 limestone to 13 of anhydrous gyps : deducting the si- 

 lex previously found. The filtered solution to which 

 the washings were added, was concentrated by evapo- 

 ration, which occasioned a slight precipitate (about 4^th) 

 of sulphat of lime : it was then treated with carbonat 

 of ammonia for the alumina, and with carbonat of pot- 

 ash for the magnesia as before. 



The component parts of the stones sent to me, were 

 ascertained on the average of these two methods. 



The limestones transmitted to me, bore evident 

 marks of contiguity to primitive strata. The colour- 



