172 FLUORIC ACID AND ITS COMPOUNDS. 



fore I thought of evaporating the whole liquid 

 to dry ness. I found traces both of fluoric acid 

 and of barytes in the liquid, whatever proportion 

 of the two salts I mixed ; it was the same thing 

 with the fluate of lime. To expel these two 

 salts completely, we must evaporate the liquids 

 containing them to dryness. Then they become 

 insoluble, and we can easily determine by means 

 of a little water whether any of the fluate of 

 soda, and of the muriate of lime, or muriate of 

 barytes originally employed, still exist in the 

 dry salt formed. 



(^') * tr * ec * wnetner solutions of 5*%5 grains 

 of fluate of soda, and 2O75 grains of nitrate of 

 lead would completely decompose each other, 

 but the experiments, though frequently repeated, 

 led to no satisfactory results ; for I could detect 

 both fluoric acid and oxide of lead in the resi- 

 dual liquid, whether I employed the salts in 

 these proportions, or increased or diminished 

 the quantity of fluate of soda. I was not at that 

 time aware of the effect produced by evaporating 

 the mixture to dryness, and after I became 

 aware of it, my stock of fluate of soda was too 

 far exhausted to allow me to resume my experi- 

 ments with nitrate of lead, without the risk of 

 not leaving enough to determine the atomic 

 weight of fluoric acid exactly, by means of mu- 

 riate of lime and muriate of barytes, which I 

 considered as of most importance. 



16 



