IQ2 DR WILSON ON THE SOLUBILITY OF 



have been a decrease in the proportion of fluoride, water having washed it out, 

 and dissolved it away. We naturally turn for light on this problem to the con- 

 sideration of the question, What proportion of fluorine is found in the bones of 

 existing animals ? Here, however, Ave are at once met, as has been already stated, 

 by the most contradictory declarations on the part of able chemists ; some affirm- 

 ing that fluorine is found in all bones ; others, that none can be detected in any. 



When it is considered how extremely simple the process of testing for fluorine 

 is, and how little room there is for difference in manipulative dexterity aflecting 

 the result, I am constrained to admit, that, in the meanwhile at least, we must 

 refuse to fluorine the character of being a constant ingredient of bones. On the 

 other hand, it is certainly a very common one, more frequently present than ab- 

 sent ; and we may encourage the expectation, that future researches will explain 

 satisfactorily the cause of failure where negative results have been obtained, and 

 prove fluorine to be an ever-present constituent, not only of bones, but of other 

 animal tissues.* 



The suggestion, accordingly, of Liebig, that fossil bones contain only the 

 fluorine which was added to them whilst parts of living structures, may be found 



* Certain of the recent observers have endeavoured to reconcile the conflicting statements of their 

 predecessors in rei'erence to this subject, but with little success. Dr Daubeny conceives that the failures 

 may have arisen, in part, from the bones examined not having been deprived of their gelatine before 

 being tested for fluorine, so that the animal matter prevented the hydrofluoric acid from acting on the 

 glass.* But on the one hand, Fourcroy and Vauuueun, who were unsuccessful searchers for the 

 element in question, pointed out long ago the necessity of burning away the gelatine as a preliminary 

 step, and always did so before looking for fluorine.f On the other hand, Mr Middleton, who found that 

 substance abundantly in bones, simply broke the latter into small fragments, and heated them with con- 

 centrated sulphuric acid. He states, moreover, that the time occupied by each experiment was only 

 between five and ten minutes.J Dr Daubeny refers likewise to the presence of salts of volatile acids 

 and salt radicals, such as chlorides and carbonates, from which hydrochloric and carbonic acids are evolved 

 when sulphuric acid is poured on the bones, and which sweep away the hydrofluoric acid before it has 

 time to corrode the glass. He has accordingly described a method of procedure which gets rid of the 

 volatile bodies in question, but only at the risk of losing, in the liberal washings prescribed, much of the 

 fluoride of calcium. It cannot be doubted that the acids which accompany the hydrofluoric, when sul- 

 phuric acid is poured upon burned bones, dilute and carry away the body sought for. But Fourcroy 

 and Vauquelin's experiments, which were made by distilling bones with sulphuric acid in glass vessels, 

 could have been but little aff'ected by this source of fallacy ; and Behzelius' successful results were 

 oljtained in the very same way. 



After trying Daubeny's process several times, I am constrained to acknowledge that I did not find 

 it give any better results than the simpler one previously in use. If it be deemed requisite to get rid of 

 the carbonic acid of bones before testing for fluorine, I believe it could be done most efiicaciously by 

 digesting them, after being burned and reduced to powder, in a solution of tartaric acid, and, after the 

 whole carbonic acid had been expelled, drying up the mass. 



Eees, taking the opposite view from Daubeny, has endeavoured to prove that, where fluorine 

 has been supposed to be present, it was in reality phosphoric acid that corroded the glass. § He acknow- 

 ledges, however, that this explanation applies only to those cases where the bones were distilled with 

 sulphuric acid, and the product of distillation evaporated to dryness in glass vessels. He regards as un- 

 exceptionable, experiments made with platina crucibles covered with waxed glass ; and as Middleton's, 

 Daubeny's, and my own trials were made in this way, and distinct corrosion or etching obtained, his 

 suggestion must be considered as leaving the subject where it found it. 



* Chemical Society's Memoirs, vol. ii., p. 100. t Annales tie Chimie, tome Ivii., p. 38. 



J Memoirs of Chemical Society, vol. ii., p. 135. § Kdin. Phil. Journal, vol. xxviii., p. 93. 



