290 Dr Daubeny on the Occurrence of Fluorine 



perfectly plausible, if the concurrence of this ingredient had been 

 casual, or had been limited to bones found in rocks of a certain age 

 or composition, seemed rather a violent one, when extended to those 

 of all ages and formations, being scarcely reconcileable with the rarity 

 of the mineral itself in the waters of springs, and its sparing solu- 

 bility in most re-agents. 



These difficulties that occurred to my mind, no less than the 

 weight I attached to the positive testimony of the great Swedish 

 chemist, in favour of the existence of fluorine in recent bones, in- 

 duced me to consider, whether it might not be possible that certain 

 circumstances had operated in the mode of conducting the experi- 

 ment, by which the presence of fluorine, in the hands of the chemists 

 who adopt the opposite conclusion, escaped detection. 



And, on further investigation, it appeared to me, that two ingre- 

 dients naturally present in recent bones might have interfered with 

 the result in the instances alluded to. 



The first of these is animal matter, which, owing to the strong 

 affinity it possesses for fluorine, may arrest its escape, and thus pre- 

 vent it from coming into contact with the glass ; the second, salts con- 

 taining any volatilizable ingredient, such as the carbonic or muriatic 

 acids, which would be disengaged by the same agent by which the 

 fluorine was set at liberty, and which, escaping in a rapid current, 

 might carry the latter along with them, before it could have time 

 to exert any sensible action upon the glass suspended over it. 

 Accordingly, I found, that whilst one-tenth of a grain of fluor spar, 

 mixed with more than 100 grains of any earthy mineral, occasioned, 

 under the action of sulphuric acid, an easily discernible, though 

 faint con-osiun, on the exposed parts of the glass, the same quantity 

 produced no effect whatever, when mixed with 5 per cent, of carbo- 

 nate of lime, or with a little gelatine ; and that half a grain of 

 fluor spar, and the earth, when mixed with gelatine, caused a trace 

 on glass not much more distinct than that occasioned by one-tenth 

 ef a grain without this admixture. 



In testing, therefore, the bones and teeth which I had obtained 

 for examination, I did not choose to content myself with merely 

 adding sulphuric acid to the pulverized specimen, but I began by 

 burning off all the animal matter ; and then, finding that carbonic 

 acid still in part remained, I dissolved the earthy residuum in muri- 

 atic acid, and threw down, by means of caustic ammonia, the earthy 

 phosphates. 



The latter, after being well washed and dried, were treated with 

 concentrated sulphuric acid in a platina crucible, covered over by a 

 plate of glass, shielded, except on the parts intended to be acted 

 upon, by a coating of wax ; but no artificial heat was applied, as the 

 sulphuric acid, by its action upon the phosphate, raised the temper- 

 ature sufficiently to expel whatever fluoric acid might be present in 

 the specimen. 



