Count de Bourn on on BardtgUone. 85*7 



Haiiy. I have however been able to perceive only a simple refrac- 

 tion in this substance. 



C. Chemical, 



Action of Acids. None, when the bardiglione is pure. 



Action of Heat. A moderate degree of heat renders such of its 

 varieties as are indeterminate of a dull white colour ; but has no 

 such effect on those that are crystallized ; yet when the crystalline 

 variety of the salt-works of Bex, enclosed in a mass of compact 

 bardiglione mixed with gypsum and sea-salt, is exposed to heat, it 

 gives both to its crystal and to their fragments a whitish tint, fre- 

 quently accompanied with a pearly lustre. 



When the heat of the blowpipe is applied to the thin edges of 

 this substance, it appeared to me to act in the same manner as it 

 does on gypsum : the bardiglione passing, without any ebullition, 

 into a very friable white enamel. The resistance of this substance 

 to fusion, when tried on large pieces, added to the friability of the 

 enamel, is no doubt the reason why several mineralogists have said 

 it was infusible by the blowpipe ; but if its action be applied, as I 

 have mentioned, to the thin edges, their blistered appearance in- 

 stantly demonstrates its fusibility. 



Analysis. In the first analysis of bardiglione, Klaproth found 

 1 5 parts of sea-salt, 27 of gypsum, and 58 of sand ; but the speci- 

 men analysed by him must certainly have been very impure. 

 Vauquelln, after having freed it from the sea-salt, which is foreign 

 to its composition, found it to consist of 40 parts of lime and 60 of 

 sulphuric acid. 



