A. A. Ramsay 285 



till bumping was severe. The precipitate was filtered off, washed well 

 with water, and on drying weighed 2-210 grams. This was marked 

 preparation 8a. The filtrate from which the last mentioned prepara- 

 tion (8a) was obtained, was further evaporated on the water bath to 

 small bulk but not to dryness. On standing for two days the mass 

 crystallised. This mass was placed on a filter paper and washed with 

 water. The washings contained much lime and phosphoric acid. The 

 filter paper and contents were placed in a water oven to dry but the 

 paper blackened and then charred. This last product therefore appears 

 to be an acid calcium phosphate; the weight would be about 1-1 gram. 

 The result of the chemical analyses of these various preparations 

 will now be given. 



Preparation No. 7 (3 equivalents CaO: 1 equivalent P2O5) was found 

 to consist of : 



Lime (CaO) 48-61 



Phosphoric acid (P2O5) 42-48 



Water ... ' 8-91 



100-00 



By calculation the above numbers correspond to a mixture of: 



CaO H,0 P.Oj Water 



Dicalcic phosphate (CaO)2H20P205... 3-297 0-530 4-180 — - 8-007 



Tricalcic phosphate (CaO)3P205 ... 45-313 — 38-300 — = 83-613 



Water of crystallisation (H/)) ... — — — 8-380 = 8-380 



48-610 0-530 42-480 8-380 =100-000 



If all the water of crystallisation be associated with the dicalcic 

 phosphate, the composition of this would correspond to the formula 

 (CaO)2 . H2O . P2O5 . 15-8H20 or CaHP04 T-OHgO. 



If as is more probable, the water of crystallisation is shared by both 

 di- and tricalcic phosphates, and assuming that CaHP042H20 is the 

 particular form of dicalcic salt present, then the formula of the tricalcic 

 phosphate present is (CaO)3P205 1-29H20. Thus : 



Dicalcic phosphate (CaO)2H20Po064H20 ... 10-127 

 Tricalcic phosphate (CaO)3P205l-29H20 ... 89-873 



100-000 



Preparation No. 8 (2 equivalents of CaO : 1 equivalent P2O5) was 

 found to consist of : 



Lime (CaO; 46-36 



Phosphoric acid (PjO 5) 41-77 



Water 11-87 



10000 



