upon Tri-calcie Phosphate. 47 
os ie IE Iii. IV. Vv. 
Ca3(PO,). |10°000 grms.|10-000 grms.|10°000 grms.|10°000 grms. |10-000 grms. 
H,S0, o143.. * 3-748 Ht 3°209. * 3209 = 3°2 
FOUND, soluble. 
CaSO, 2°124 grms,| 2°459 grms.} 2°960 “ | 1140 grms, 
CaH,(PO,), st eas FOTT 1334 *Sn01* 3°562 grms. 
H;P0, 209." 25. = i eee 448 * 
Insoluble. 
2°168 s.| 2°784 grms.| 1°504 grms.| 3466 “ 
CaHPO, 6°467 ne C2208 5°415 5°493 
Ca;(PO,)2 | 1065 “ | -g03 “ | 1899 “ | 1-947 « 
It will be seen that the amount of di-calcic phosphate 
increases and that of mono-calcic phosphate decreases the longer 
the mixture stands and the higher the temperature to which it 
is exposed. 
The following table shows the decrease of mono-calcic phos- 
phate still more clearly. 
If the reaction take place according to the equation 
Ca,(PO,),+2H,SO,=CaH,(PO,).4+2CaS0, 
one molecule of sulphuric acid should render soluble one mole- 
cule, or its own weight, of phosphoric acid. The fourth line of 
the table gives the per cent of this theoretical quantity which 
was actually found. 
LG Il. i. LY: % 
Applied, Ca;(PO,), |2°784 grms.'2°972 grms./4°377 grms.|4°377 grms. |4°377 grms. 
woe? eal Os) Geer grm grm ae 
2 
204 Ps: ia0e:: & 2 2405) “ 
Found H;P0, “420 5b5 tt 507 20 «61-305 
82 “i 
& of theoret. H,PO,| 32:24 371% 395% 361% 92°3 % 
_ 4n order to be sure that these differences were not due to 
incomplete washing a second set of experiments was made with 
Smaler quantities. The tri-calcic phosphate was mixed with 
thin paste, the sulphuric acid added, the mixture 
Well stirred, and treated as follows :— 
I. Stood 3 hours at 100° C. 
IL “« “ « ordinary temperature. 
IIL T3 4 hour “ 73 (73 
IV. “ 65 minutes at “ ss 
It was then filtered on the pump, washed with cold water till 
the washings showed only a very faint reaction for phosphoric 
acid with magnesia mixture, the filtrate diluted to 500 cc. and 
eth — the phosphoric acid determined by the molybdic 
