FLUORIC ACID. 1 69 



evaporated in a silver crucible till the rluate of 

 soda crystallized. It formed transparent crusts 

 very like ice, having a saline but not a strong 

 taste ; it was heated in a silver crucible till its 

 water of crystallization was expelled. In this 

 state it formed opaque white crusts, which be- 

 came again transparent when put into water. 

 The salt had been prepared with so much care, 

 that there was no reason to doubt of its purity. 

 In order to be sure that it was quite anhydrous, 

 the crucible containing it was raised to a low red 

 heat before every experiment. 



(1.) 5*5 grains of this salt (which was neu- 

 tral) were dissolved in a little water in a pla- 

 tinum crucible. 



Into another platinum crucible were put 6-25 

 grains of pure calcareous spar, (equivalent to 

 3-5 grains of lime,) which were dissolved in di- 

 lute muriatic acid ; the solution evaporated to 

 dryness, and the salt which was left was dissol- 

 ved in water. 



These two liquids being mixed together, a 

 double decomposition took place, fluate of lime 

 being deposited, and muriate of soda remain- 

 ing in solution. The crucible containing the 

 whole contents was put on the sand bath, and 

 the whole liquid evaporated to dryness by means 

 of a very gentle but long continued heat. A little 

 hot distilled water was then poured on the dry 

 saline mass, and allowed to remain digesting on 



