Dr. Babington on Spontaneous Evaporation. 317 
The sixth proposition is rendered probable by the following ex- 
periment, in which solutions are employed of acetic, nitric, sulphuric, 
and hydrechlorie acids, combined respectively with potassa, soda, 
and ammonia, in the proportion of 100 grains of the salt to 1000 
grains of water. After the expiration of 10 hours and 20 minutes, 
the solution of the three acetates lost respectively, for the potassa 
salt 35 grs., for the soda salt 35 grs., and for the ammonia salt 
28 gers. In the solutions of the three nitrates, the loss was re- 
spectively 24, 25, and 25. In the solutions of the three sulphates, 
the loss was 30 grs., 37 grs., and 29 grs. respectively, while in the 
solutions of the hydrochlorates it was 17, 18, and 19 grains. 
The seventh proposition is proved by an experiment in which a 
solution of 100 grains of carbonate of potassa dissolved in 1000 
grains of water is compared with a like solution of bicarbonate of 
potassa. In ten hours the solution of: the carbonate lost 45 grains, 
while that of the bicarbonate lost only 36 grains. In comparing 
like proportions and quantities of sulphate and bisulphate of potassa, 
the respective losses in 13 hours were, for the former 53 grains, for 
the latter 45 grains. Similar comparisons of the acetate and bin- 
acetate of ammonia, phosphate and biphosphate, sulphate and 
bisulphate of potassa, tartrate and bitartrate of soda show like 
results. In the course of investigating this proposition it was 
remarked incidentally that in all the salts examined, with the single 
exception of carbonate and bicarbonate of soda, the bin-acid solution 
(the proportion by weight of salt to water being equal) is of less 
specific gravity than the mono-acid solution, though possessing a 
greater power of retarding evaporation. 
The eighth proposition, which seems extraordinary and even 
paradoxical, is proved by an experiment in which saturated solutions 
of—l1, ferro-cyanate of potassa, 2, bitartrate of potassa, 3, sulphate 
of copper, 4, chlorate of potassa, and 5, distilled water, were com- 
pared. In 9 hours and 20 minutes, their losses by evaporation were 
respectively 34 grs., 38 grs., 34 grs., 29 grs., and 29 grs., where we 
perceive that in the chlorate of potassa solution there has occurred 
no retardation at all, while in the following experiment, in which 
120 grains of each of the salts examined were dissolved in 1200 
grains of water, namely,—1, solution of sulphate of copper, 2, solu- 
tion of ferro-cyanate of potassa, 3, solution of carbonate of soda, 
and 4, distilled water, the number of grains lost by evaporation after 
153 hours’ exposure were,—1, 120 grs.; 2, 113 grs.; 3, 106 grs.; 
4, 103 grs. 
It is thus perceived that in all the three solutions a more rapid 
evaporation had taken place than in distilled water alone. 
One or two other propositions are in process of investigation. 
The paper concludes with a table of the freezing-points, boiling- 
points, and specific gravities, as well of weak as of saturated solutions, 
of the salts which have been submitted to examination. 
