OF STEAM ARISING FllOM BOILING SALT SOLUTIONS. IT" 



exactly the same as that of the solution. This, I believe, is the first 

 occasion on which the above important fact has been experimentally 

 established. Philosophers had, indeed, asserted that the temperature 

 of such steam should be, or would Ije, the same as that of the solu- 

 tion, but without any experimental proof. Gay-Lussac's assertion,. 

 " the temperature of the vapour furnished by any liquid is exactly 

 the same as that of the liquid layer in immediate contact with the 

 vapour," is based upon the knowledge of the facts derived from the 

 study of simple liquids, such as water, alcohol, &c. ; for no direct 

 experiments had been made by him, or any other investigator before 

 him, upon the temperature of the steam arising from a boiling salt 

 solution which established the truth of that assertion. So far as 

 direct experimental evidence is concerned, he had, I think, no good 

 reason for extending his remarks to the case of a salt solution.. 

 Faraday thought he had proved Gay-Lussac's assertion to be correct 

 in the case of salt solutions also, but upon evidence not at all con- 

 vincing. Magnus could not show that the temperature of the steam 

 is exactly the same as that of the solution. " That, however, it (the 

 steam) possesses the same temperature as the solution I cannot prove,, 

 and I doubt whether it can possibly be proved," he says. The grounds 

 for such doubt have now been remo\ed by the experiments above 

 described, the secret of the success lying in the fact that the walls of 

 the steam- chamhcr must he ahovi 100^, and yet below the temperature of 

 the solution, and that, at the same time, a sv^cient quantity of steam must 

 escape from the solution to ensure that these walls shall hare no material 

 cojling ef'ect vpon the steam. To meet this condition the quantity of 

 steam evolved from the boilin«- solution itself is not sufficient, and 

 hence the necessity of passing steam from without into the boiling 

 solution. 



That the quantity of steam merely arising from a boiling salt 



