Fluorine in Hecent as well as in Fossil Bones. 125 



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

 strong affinity it possesses for fluorine, may arrest its escape, 

 and thus prevent it from coming into contact with the glass; 

 the second, salts containing any volatilizable ingredient, 

 such as the carbonic or muriatic acids, which would be dis- 

 engaged 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. Ac- 

 cordingly 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 dis- 

 cernible, though faint corrosion on the exposed parts of the 

 glass, the same quantity produced no effect whatever, when 

 mixed with 5 per cent, of carbonate 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 of a grain 

 without this admixture. 



In testing, therefore, the bones and teeth which I had ob- 

 tained 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 the carbonic acid still in part remained, I dis~ 

 solved the earthy residuum in muriatic 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 phos- 

 phate, raised the temperature sufficiently to expel whatever 

 fluoric acid might be present in the specimen. 



The glass was allowed to remain as a cover to the platina 

 crucible for at least two hours, and in order to ensure the 

 condensation upon it of the hydrofluoric vapour, a rim of wax 

 was placed round the margin of the upper surface of the glass, 

 by means of which a small portion of water might be kept 

 the whole time in contact with it, so as to maintain a suitably 

 low temperature. 



That these precautions were not unnecessary I satisfied 

 myself, by observing the difference in the degree of corrosion 

 produced by a fossil bone given me by Dr. Buckland from 

 the cave of Kirkdale in Yorkshire, when thus purified from 

 the animal matter of which its long interment had not yet de- 

 prived it, as well as of its carbonic acid, as compared with the 



