TEMPKKATURE OF VAPOUR FROM BOILING SALINE SOLUTIONS. 



219 



to use a double-walled vessel which contained the boiling 

 solution not only between the walls but above them, and 

 that he had to heat the thermometer previously to a tem- 

 perature higher than the solution. Sakurai criticises these 

 experiments adversely, pointing out that as the walls were 

 of highly conducting material, the steam would be heated 

 by them. In fact he says, it can be shown that by keeping 

 the walls of a vessel at 110° the steam issuing from boiling 

 water itself indicates a temperature almost equal to the 

 walls. Rudberg in 1835 published the results of a long series 

 of observations from which he con- 

 cluded that the temperature of the 

 vapour arising from boiling salt 

 solutions was exactly the same as 

 that from the pure solvent, i.e., 100° 

 under ordinary pressure. Since his 

 time many papers have been pub- 

 lished, some holding one view and 

 some another. 



In the experiments carried out by 

 Sakurai the solution was boiled in 

 a flask F (see Fig. 1) the walls of 

 which, above the level of the solu- 

 tion, were enclosed in a glass 

 cylinder J J, so as to form a jacket. 

 This jacket was filled with hot 

 vapour at a slightly lower temper- 

 ature than the solution, so as to 

 reduce to a minimum radiation 

 losses from the vapour arising from 

 the boiling solution. The vapour 

 was derived by boiling a liquid jn a 

 separate flask. It entered the jacket 

 by the tube u and passed out by r 



Fig. 1. 



