282 Oil the Composition of (liferent inorganic Bodies. [April, 



volume, and became gelatinous and semi-lransparent, asby asolu- 

 lion in the acid without decomposition. No effervescence took 

 place. At a higher temperature, the mass began to exhale 

 vapours of fluoric acid in abundance, became white, and lost its 

 transparency in proportion as the fluoric acid was disengaged. 

 The sulphate of lime was then exposed to a red heat to drive off 

 the excess of sulphuric acid. It was white as snow, and weighed 

 17"363 gra'mmes. I then added a new quantity of sulphuric acid 

 which 1 allowed to digest for some hours with the sulphate, and 

 the excess of acid was then entirely dissipated by the tire. The 

 weight of the sulphate of lime was n»it in the least increased. 



Ten grammes of fluate of lime treated in the same way pro- * 

 duced in a second experiment 17-368 of sulphate of hme, dried 

 in a red heat. According to these experiments, fluate of lime is 

 composed of 



Fluoric acid 27-863 100-0 



Lime 72-137 258-9 



100-000 



The 258-9 of lime contain 72-7815 of oxygen, which conse- 

 quently ought to represent the real capacity of saturation of 

 fluoric acid. 



In examining tliese experiments, we find that both the inac- 

 curacies of the method of operating, and the foreign substances 

 in the fluate of lime, ouaht all to concur to render the quantity 

 of sulphate of lime obtained too small; and that no other circum- 

 stance, except the impurity of the sulphuric acid, could increase 

 the quantity of that salt. To verify this point, I evaporated in 

 a platinum crucible 150 grammes of ihe sulphuric acid employed, 

 but the weight of the crucible was not altered. It is obvious 

 then that the analysis of fluate of lime has given a more exact 

 result than that of the other fluates analysed above. The cir- 

 cumstance that the fluate of lime becomes transparent, and 

 appears to combine v.ithout decomposition with cold sulphuric 

 acid, ought to o-uarantee the absence of silica, as the slightest 

 trace of that earth determines the immediate disen2:ai>ement of 

 silico-fluoric gas, which is manifested by a greater or smaller 

 effervescence, which sometimes occasions the mass to run. over 

 the vessel in which it is contained. It is probable that the 

 reason why the artificial fluates have given the ratio of the acid 

 to the base greater than the fluate of lime is, that they contained 

 a small quantity of silica which could not be entirely separated 

 from them, and which, in the analytical experiments, accompa- 

 nied the fluoric acid. 



When we seek to determine from the capacity of saturation 

 of this acid wh-at is the quantity of oxygen wiiich it should con- 

 tain, considerinc; it as an acid with oxyoren, whose combustible 



i 



