IgO DR WILSON ON THE SOLUBILITY OF 



occur in the bodies of animals, as it does in those of the inhabitants of other 

 localities. The experiment in question was made in Edinburgh. 



It could not be doubted, after the facts I have detailed, that fluorine would 

 be foimd in the two great formative liquids of the animal body, blood and mDk ; 

 I have found it in both. So far as I am aware, it has hitherto been overlooked 

 in all the analyses that have been made of these liquids ; probably it has not 

 been sought for. 



I employed the blood of the ox, and in two cases obtained markings on glass, 

 which only become visible when breathed upon, but are then quite manifest. 

 In the third the glass was distinctly, though faintly, corroded. 



That others may know exactly how the experiment was made, I may men- 

 tion, that in the most successful case, about 128 ounces of blood were taken, which 

 had been freed, by stirring, from much of its fibrine, and was boiled till the liquid 

 solidified. The broken coagulum was burned in a large crucible, the ashes boiled 

 with dilute muriatic acid, and the liquid filtered and evaporated to dryness. The 

 residue was then heated to redness to expel chloride of iron, and afterwards 

 washed with a small quantity of water, sufficient only to remove the accom- 

 panying chloride of sodium. The insoluble matter, which was in brilliant metallic 

 crystalline scales, was reduced to fine powder, and heated with Nordhausen 

 sulphuric acid, in a basin covered by waxed plate-glass. As the experiment per- 

 formed in this way gave the fluorine only or chiefly of the serum, we may expect 

 a still more decisive result to be obtained when the whole blood is taken. But 

 it is so difficult to burn the fibrine of blood, that I was content, in a first trial, to 

 experiment chiefly with the serum. As already mentioned, where the entire 

 blood was made use of, glass was marked, but not corroded. Both of the trials, 

 however, with the entu-e blood, were conducted so as to involve many washings, 

 which were avoided in the third and most successful experiment. 



In examining milk, I thought to have saved myself the trouble of boiling down 

 large quantities of that liquid by using cheese, which was burned, and the ashes 

 digested in muriatic acid. The filtered solution was supersaturated with ammo- 

 nia, and the precipitate whicii fell (consisting chiefly of phosphates), washed, dried, 

 and tested Avith Nordhausen acid and glass. In three cases I totally failed to 

 detect fluorine whilst operating in this way. I was not more successful with 

 two qiiantities of millv treated similarly. I mention these failures to shew the 

 necessity of avoiding methods which imply much washing upon filters, when 

 fluoride of calcium is sought for. The large quantity of liquid made use of in the 

 course of the process referred to, may have held in solution and carried away all 

 the fluoride present ; especially as the addition of ammonia could only separate 

 fluoride of calcium previously dissolved by an acid. In the last and successful 

 attempt to detect fluorine in milk, the hydrochloric solution was neutralised with 

 ammonia and precipitated by nitrate of baryta. The precipitate, which was 



