The Latent Heat of Evaporation of Aqueous Salt Solutions

The Paper records the results of a research into the latent heat of evaporation of steam from salt solutions. The experimental method was to supply a measurable quantity of heat electrically, through a small lamp to the solution boiling inside a calorimeter. The latter was placed within a double-walled vessel surrounded by a solution boiling at the same temperature; and the steam from the inner vessel passed out through a tube into a detachable condenser, which was weighed at intervals. Measurements were made with the solutions of six different salts. Theoretical considerations show that the difference between the measured heat L, and l T the known heat of evaporation of water at the same temperature, is the heat of solution Q; and the present results indicate that for salts of the same acid Q is proportional to the concentration. For unsaturated solutions of KCl and NaCl the interesting result is found that the heat of evaporation is approximately constant for all concentrations until saturation is reached.