X48 DR WILSON ON THE SOLXTBILITY OF 



chemical forces can explain the phenomenon. The great German chemist, also, 

 (whose view may be the true one,) will probably modify his opinion, when he 

 finds that fluoride of calcium is soluble in water. 



Mr Middleton's supposition that all bones contain two per cent, of fluor, is 

 certainly untenable, and so is his belief that bones invariably gain fluorine whilst 

 undergoing fossilisation ; but he brought satisfactorily to the test of experiment 

 his view that fluoride of calcium may reach the bones both of living and dead 

 animals through the medium of water. His experiments were not made with 

 aqueous solutions, in which a mere trace of fluoride could at best be expected to 

 be present, but Avith sedimentary deposits, of natural and artificial origin. " I 

 was led," says he, " to institute a series of experiments on aqueous deposits 

 of different ages, and I found, that, with one exception (a pure but incompact 

 stalactite of carbonate of lime), fluorine exists in all, from the most recent deposit 

 down to the old red sandstone, and that it is present in the older in larger pro- 

 portion than in the neAver beds. I think it is, therefore, beyond a doubt, that it 

 is present in water, though, perhaps, in very minute quantity. What its solvent 

 may he I know not j but that it is so held in solution my own experiments have 

 demonstrated ; and if they had not, the simple fact that the blood conveys it to 

 the bones, would, I apprehend, sufficiently refute any scepticism on the subject."* 



It may justly be questioned, whether the fact of a substance being soluble in 

 a highly complex fluid like blood, would entitle us to infer that it was equally 

 soluble in pm-e water. But it is singular that Mr Middleton, holding such a view, 

 and after finding fluorine in so many aqueous deposits, should not have endea- 

 voured to dissolve the fluoride of calcium in water. He was, doubtless, prevented 

 from making any trials on the subject by the universal statement of chemists, that 

 the salt in question is quite insoluble in water. 



2. Of the Solubility of Fluoride of Calcium in Water. 

 Many substances are spoken of by chemists as insoluble in water which are. 

 nevertheless, known to possess a certain slight solubility in that fluid. But 

 fluoride of calcium has been considered so well entitled to the character of total 

 insolubility, that our most accurate analysts, as Berzelius and Rose, have pur- 

 posely converted fluorine into this salt in their quantitative determinations of the 

 former, and have washed the latter freely with water, and, as they believed, with- 

 out its suffering any loss. Their example has been followed by all other analysts, 

 and the fact supplies a better proof than any quotation of individual authors could 

 do, that fluoride of calcium has been considered quite insoluble in water. Rely- 

 ing implicitly on the truth of this belief, I sought for a solvent of fluor-spar which 

 could retain it in union with water, and carry it into the tissues of plants and 



* Quarterly Journal of Geology, vol. i., p. 215. Mr Middleton's other papers on fluorine are 

 in the Chemical Society's Memoirs, vol. ii., p. 134 ; and in the London Phil. Mag., No. 164, p. 14. 



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