46 H. P. Armsby— Reaction of Sulphuric Acid 
Art. VIL—On the Reaction of Sulphuric Acid upon Tri-caleie 
Phosphate; by H. P. Anmssy. 
a 
THE following experiments were undertaken to ascertain the 
influence of temperature and time on the reaction between one : 
molecule of sulphuric acid and one of tri-calcic phosphate. __ 
he materials employed were precipitated tri-calcic phos 
phate and a solution of sulphuric py i : 
0°8784 grms. H,SO,. . 
The tri-calcic phosphate was prepared by precipitation from — 
an ammoniacal solution of calcium chloride by di-sodic phos- — 
phate, the precipitate being washed with cold water. An anal a 
ysis gave :— | 
containing in 1 ¢.¢, 
| Re Cine sre oie 53°82 
8 Aaa s ye not determined, 
Although washed by decantation till the washings gave 10 : 
precipitate with silver nitrate the substance still contained : 
traces of soluble phosphoric acid, probably as phosphate of soda. | 
e experiments were conducted as ie; sath a weighed quan- 
tity (generally about five grms.) of tri-calcic phosphate was mixed | 
a 
re eee 33°73 per cent. - 
(73 “ tam : 
by rubbing in a mortar with the equivalent quantity of sulphu- 
ric acid, and treated as follows :— a 
I. Stood 23 hours at 100° C. 
“ “ce sc “ 4 
we 34 oe ae “ ordinary per — 
IV. * heer. & S « 
Vv. “ 5 minutes at “ = 
i The mixture was then washed with cold water till the wash- 
ings ceased to show an acid reaction, the filtrate diluted to 500° 
acid, the excess ‘of the latter over that required to form tri-calci¢ 
phosphate being considered to exist as the only other insolubl 
