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



Determination of the amount of Calcium in Bone. 



The filtrate from the last operation is treated with solution of 

 NH 4 Cl, so as to precipitate completely, as AgCl, the silver which 

 it contains ; the nitrate is saturated with ammonia, and then acetic 

 acid is added so as to cause complete solution of the precipitate. 

 In the case of old bones which have been macerated or buried, 

 a certain quantity of phosphate of iron is present in the bone ash, 

 and it forms that part of the ammonia precipitate, just mentioned, 

 which is not dissolved by an excess of acetic acid. It may be 

 collected on a filter, washed, dried, ignited and weighed as Fe 2 (P0 4 ) 2 . 

 ' From the acetic acid solution of the ammonia precipitate, the 

 calcium is thrown down by adding solution of ammonium oxalate. 

 The fluid, with the precipitate, is heated on a water-bath, set aside 

 in a warm place for 24 hours, and then thrown on a filter of which 

 the amount of ash is known ; the filtrate is collected and kept. The 

 precipitate is washed with water holding a little ammonia in solution. 

 It is then dried, and the precipitate and filter-paper with adhering 

 precipitate are separately ignited, as directed in works on quantitative 

 analysis. 100 parts of the resulting CaCO 3 correspond to 40'00 

 of Ca. 



Determination of the Magnesium. 



The filtrate from which calcium has been precipitated by means 

 of ammonium oxalate is evaporated to a small bulk. It contains 

 all the magnesium of bone in the form of phosphate, which is preci- 

 pitated as ammoniaco-magnesian phosphate (Mg]SH 4 P0 4 + 6H 2 0) 

 on saturating with ammonia. With this object an excess of ammonia 

 is added and the fluid is set aside for 24 hours in a warm place ; 

 it is then filtered through a small filter, the precipitate is washed 

 with ammoniacal water, dried and ignited. 



100 parts of Mg 2 P 2 7 correspond to 21'622 of Mg. 



Determination of Phosphoric acid. 



The filtrate from the precipitate of ammoniaco-magnesian phos- 

 phate in the last operation is now treated with magnesia mixture 1 

 and set aside for 24 hours. Again a precipitate of ammoniaco- 

 magnesian phosphate forms, which corresponds to all the phosphoric 

 acid not combined with magnesium. The precipitate is treated as in 

 the last operation. 



100 parts of Mg 2 P 2 O 7 correspond to 78'37872 of 2(P0 4 ). 



1 " Magnesia mixture is made by dissolving one part of recrystallized magnesium 

 sulphate and one part of pure ammonium chloride in eight parts of water, and adding 

 to the mixture four parts of moderately strong ammoniac solution. The liquid is 

 allowed to stand for a few days in a corked flask; it is then filtered and preserved 

 in a well-stoppered bottle." Thorpe's Quantitative Chemical Analysis, p. 111. 



