539 
of Edinburgh, Session 1877 - 78 . 
5. A weighed quantity of solid calcium chloride was dissolved in 
a measured quantity of water, and the rise in temperature noted. 
This was 15° Fahr. 
6. The same quantity of calcium chloride was dissolved in strong 
hydrochloric acid and the rise in temperature also noted. This was 
6° Fahr., being a difference of 9°, accounted for, no doubt, by the 
vapourising of the hydrochloric acid gas expelled in the latter case. 
7. NaCl and CaCl 2 . — Calcium chloride, both in solution and 
solid, was added to saturated solution of common salt, and in both 
cases the sodium salt was precipitated, the calcium chloride taking 
its place in the solution. 
8. HCl and FT 2 $0 4 . — Strong sulphuric acid was added to strong 
hydrochloric acid, when the latter as gas was expelled with effer- 
vescence. 
9. CaSOfICl and H 2 SO r — Strong sulphuric acid was added 
to a saturated solution of calcium sulphate in hydrochloric acid, 
when calcium sulphate was precipitated, and hydrochloric acid gas 
expelled. 
I next looked about for two solvents which would dissolve the 
same substance, and yet precipitate it when mixed. These results 
I found with sulphuric acid, water, and calcium sulphate. 
10. CaSO 4 , Water , and H 2 SO r — To a saturated solution of 
calcium sulphate in water was added some strong sulphuric acid. 
On cooling, the calcium sulphate was precipitated. 
11. CaSO±, H 2 SO± and Water .. — To a saturated solution of 
calcium sulphate in sulphuric acid was added water. As before, on 
cooling, calcium sulphate was precipitated. 
12. Two solutions (saturated) of calcium sulphate, one in water 
and one in sulphuric acid, were mixed when calcium sulphate was 
precipitated on cooling. 
Three experiments similar to Nos. 10, 11, and 12 were per- 
formed, only substituting clay in suspension for calcium sulphate in 
solution, and the results were similar. Clay, in sulphuric acid 
(strong), was suspended nearly as long as in pure water, but on 
mixing the liquid, or on adding sulphuric acid to the water, or water 
to the sulphuric acid, the precipitation of the clay was greatly 
accelerated. 
I hope to extend these experiments to other substances than those 
