288 ANALYSIS OF MINERAL MATTERS OF BONE. [BOOK I. 



dioxide through the concentrated sulphuric acid is to dry the gas and 

 to retain the moisture in the apparatus. When the evolution of CO 2 

 has ceased, stopcock b is again opened for an instant so as to allow a 

 fresh quantity of hydrochloric acid to act upon the bone. When the 

 evolution of C0 2 has ceased and does not recommence on the addition 

 of a few drops more of the acid, the whole apparatus is placed on 

 a water bath so as to heat it gently for a few minutes. The stopcock 

 b is then opened, the stopper at the upper part of B is temporarily 

 removed and a piece of narrow india-rubber tube is slipped over the 

 upper narrow portion of the perforated stopper e. The experimenter 

 then placing the free end of the india-rubber tube in his mouth, 

 draws air through the whole apparatus for about a minute, or rather 

 until the gas which is aspirated has lost the peculiar taste of CO 2 . 

 The india-rubber tube is then taken away, the stopper of B is 

 replaced, the whole apparatus once more wiped with a clean and dry 

 cloth, placed in the balance case for half an hour, and then again 

 weighed. On subtracting the weight after, from the weight before 

 decomposition, the weight of dry CO 2 evolved is readily ascertained. 



Determination of Fluorine. 



Most chemists who have published analyses of bone have esti- 

 mated the amount of calcium fluoride indirectly, as follows. The 

 whole of the CO 2 of the bone is supposed to exist as calcium carbonate, 

 (CaC0 3 ), then the whole of the phosphoric acid which does not exist 

 as magnesium phosphate is calculated in combination with calcium. 

 In a properly conducted analysis it will be found that on adding 

 together the calcium combined with carbonic and phosphoric acid 

 and subtracting the amount from the total weight of calcium found, 

 there is a small excess of lime left, which obviously must have existed 

 in some other form of combination. This is calculated as existing in 

 combination with fluorine. 



Zalesky * determined the quantity of Fl directly, by a modification 

 of the method first suggested by Kobell. This consists in gently heat- 

 ing for a long period of time a weighed quantity of bone with strong 

 sulphuric acid and a weighed quantity of glass, the amount of silica 

 in which has been previously determined. In presence of the silica 

 and sulphuric acid all the fluorine contained in the bone unites to 

 form fluosilicic acid, SiFl 4 . The amount of fluorine present in the 

 bone is ascertained by determining the loss of weight which the glass 

 undergoes 2 . 



Calculation of the results of the Analysis of the ash of bones. 



The whole of the magnesium found is calculated as magnesium 

 phosphate (Mg 8 P 2 8 ). The amount of phosphoric acid in this com- 



1 Zalesky, Op. cit. p. 36. 



2 Kobell's original paper was published in the Journ. f. prakt. Chemie, Vol. 162, 

 p. 385. The reader who desires to know the improvements introduced by Zalesky is 

 referred to the previously quoted memoir by this author. 



