48 M. C. Lea—Dr. Vogel's Color Theory. a 
L I. Il. IV. 3 
Applied, Ca;(PO 1-751 grms. | 1-751 grms. | 1-751 grms. | 1-751 grms_— 
a HNO, ae agge | agg ee | -agge | 43g 
Found, H,PO, 172“ | 200 & 209 “ | -415 
¢ of the theoretical H,PO, | 39-2 ¢ 45°6 % avrg | 9478 
To ascertain the extent of error from incomplete washing the 
insoluble portion of I. was further washed with about 250 CC. of 
cold water and the phosphoric acid in the filtrate determined. 
Its amount was 0:018 grms. a part of which was doubtless 
due to di-calcie phosphate which is slightly soluble in water, 
though not sufficiently so to introduce any material error into 
the experiments. : 
From the above results it appears that the reaction betwee) — 
sulphuric acid and tri-calcic phosphate, when the two are present 
in the proportion of one molecule of each, passes through two 
sta; 
es, ; : 
ist. The sulphuric acid reacts on half the tri-calcic phosphate, 
producing mono-calcic phosphate. Whether free phosphoric 
acid is at first produced cannot be determined from these expert 
ments, but if it is, it must quickly disappear. : 
2d. The mono-calcic phosphate thus produced reacts more 
slowly on the other half of the tri-calcic phosphate in the mat 
ner described by Piccard (Zeitschr. fiir Chemie, ix, 545), pre 
ducing di-calcic phosphate, : 
CaH, (PO,),+Ca,(PO,),—4CaHPO,. 
A high temperature appears to favor the reaction. 
Chemi: ry of the University of Leipzig, March, 1876. 
Arr. VIIL—Dr. Vogel’s Color Theory; by M. Carzy Lea, — 
Philadelphia. 
