162 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, we 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 affecting 
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 fiuorine to be an ever-present constituent, not only of bones, but of other 
animal tissues.* 
The suggestion, accordingly, of Lirpic, 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 reference to this subject, but with little success. Dr DaupEny 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 Vavu@uELin, 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.t+ On the other hand, Mr Mippieron, 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.{| Dr Davseny 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 affected by this source of fallacy; and Brerzexius’ successful results were 
obtained in the very same way. 
After trying DauBENny’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 efficaciously 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. 
Rzzs, taking the opposite view from Davzeny, 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, 
Davseny’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 de Chimie, tome lvii., p. 38. 
t Memoirs of Chemical Society, vol. ii., p. 135. § Edin. Phil. Journal, vol. xxviii., p. 93. 

