132 



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 1, 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 arid 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 

 15 J 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. 



