On the Solubility of Fluoride of Calcium in Water, 205 



besides being tbe active organs of motion, perform, by their contrac- 

 tions, an important office in the circulation of the arterial as well as 

 venous blood ; an office which has not hitherto been described by 

 physiologists, but which appears to be capable of explaining several 

 interesting phenomena in tlie living body, of which no satisfactory 

 account has yet been given. 



3. On the Solubility of Fluoride of Calcium in Water, and 

 the relation of this property to the occurrence of that 

 Substance in Minerals, and in recent and Fossil Plants 

 and Animals. By Dr G. Wilson. 



After a preliminary reference to the existence of fluorine in recent 

 and fossil bones, Dr Wilson stated that he had made a series of ex- 

 periments with a view to discover what solvent carried fluoride of 

 calcium into the tissues of plants and animals. His first trials were 

 made with carbonic acid, which was passed in a current through 

 water containing pure fluor-spar in fine powder suspended in it. The 

 fluor was by this treatment dissolved, yielding a solution which pre- 

 cipitated oxalate of ammonia, and when evaporated left a residue 

 which, on being heated with sulphuric acid, gave off hydrofluoric acid. 



The author was, in consequence, inclined to suppose that carbonic 

 acid conferred upon water the power of dissolving fluoride of calcium. 

 But on observing that, long after the whole of that gas had been ex- 

 pelled by warming the liquid, the latter remained untroubled, he be- 

 came satisfied that water alone can dissolve fluoride of calcium, con- 

 trary to the universal statement of writers on chemistry. 



On prosecuting the inquiry, he found that water at 212° dissolved 

 more of the fluor than water at 60°, but he has not yet ascertained 

 the proportion taken up by that liquid at either temperature. 



The aqueous solution of fluoride of calcium was found to give, with 

 salts of baryta, a precipitate which required a large addition of hy- 

 drochloric or nitric acid to redissolve it. The author pointed out 

 the difficulty which must in consequence occur, in distinguishing be- 

 tween dissolved fluoride and sulphates, and suggested that fluorides 

 may have been mistaken for sulphates in the analysis of mineral 

 water. 



He referred also to the objection which must now lie against the 

 present method of determining the quantity of fluorine present in 

 bodies, consisting, as it does, in converting that element into fluoride 

 of calcium, which, in the course of the necessary analytical opera- 

 tions, is washed freely, and must be sensibly diminished in quantity ; 

 a fact which has of necessity been hitherto overlooked. Dr Wilson 

 stated that he was not yet able to suggest an unexceptionable quan- 

 titative process ; but that the fluoride of barium, being much less 

 soluble than the fluoride of calcium, might, in the meanwhile, be sub-, 

 stituted for it in the estimation of fluorine. 



