1895] Fluorine as a Test for the Fossilization of Animal Bones. 451 
distilled water added to replace loss by evaporation. There 
was, under these conditions, a notable increase in the bones, of 
fluoride of calcium, despite the slight solubility of the fluor- 
spar employed as are-agent. We then have the right to sup- 
pose that the continuous action during an indefinite time 
could produce a fluoration much more advanced than that 
shown in the experiment. The analyses or attempts did not 
succeed the same in closed vases where the bones were in the 
presence of the powder of fluorspar and of carbonate of am- 
monia of 2 grams, whether with seltzer water only, or with the 
seltzer water and sand. After three months of trial, one of the 
bones showed 0.32 and the other 0.31 of fluorine. 
The experiment was also made of the action of a copper- 
zinc couple in the mixture; but at the end of four months 
this contained still 0.80 per cent of fluorine, about the same as 
at the begininng. From these negative results we may make 
certain inductions which may be of utility in explaining the 
phenomena. 
There was realized in experiments 1 and 4 the gradual fix- 
ation of fluoride of calcium on the phosphate of lime of the 
bones, whether using fluoride of calcium in powder (of which 
a small proportion was dissolved in the water containing car- 
bonate of ammonia), or whether in producing action upon the 
bones by a small quantity of alkaline fluoride in solution. 
The alkaline fluoride can act directly upon the phosphate of 
lime in giving birth to fluoride of calcium and to a soluble 
alkaline phosphate, from which results a diminution of the pro- 
portion of the insoluble residue of phosphoric acid ; or it can 
produce action of the alkaline fluoride on the carbonate of 
lime which is found mixed with phosphate in the bone and 
which causes the formation of fluoride of calcium. 
In cases where the fluoration takes place under the sole in- 
fluence of fluoride of calcium, it ought to have for its extreme 
limit, the proportion which we observe in apatite—that is, 
about one part of fluorine to 11 parts of phosphoric acid. But 
if the alkaline fluoride intervenes, the fluoration can go farther 
and reach a proportion much higher than that of apatite. This 
was shown in Experiment No. 1, and it has been observed in 
fossil bones and in phosphates of organic origin. 
