or STEAM ARTSIXa FROTNT TIOTLTXG SALT SOLUTTOXS. H 



radiation by rapid removal of the vapour in contact with the thermo- 

 meter, can be easily effected by the expedient of com])ining the in- 

 troduction of steam from without with the boiling of the solution by 

 the lamp, the combination lieing regulated by maintaining steady the 

 temperature marked by the tliennometer in tlie solution. Ebullition 

 alone should suffire for thi.-; purp(i;e, hut the practicnl difficulties in 

 the way render it insuffi(,'ieiit. Tlie boiling would liave to be tumul- 

 tuous to generate mucli vapour, and in a short time the solution 

 would become too concentrated for the experiment to be continued 

 with convenience. On the other hand, with due regulation of the 

 steam entering from without and the height of the flame, an abun- 

 dant supply of steam can be got without impediment. Moreover, 

 irregular boiling and bumping of the solution are hoth entirely pre- 

 vented when tlie operation is worked in this manner. 



3. The walls of that part of the vessel which serves as the steam 

 chamber for the thermometer must lie sufficiently protected from 

 cooling externally, and yet, :>.t the same time, not be heated to the 

 teinperature of the steam. For if, as in Rudberg's experiments, the 

 former condition is not observed, so much of the steam is condensed 

 in keeping the walls at 100° that it is liardly possible to keep enough 

 passing over the thermomeler bulb ; while if the latter condition is 

 ignored, as in Magnus's experiments, the indications of the thermo- 

 meter may be illusory. 



The arrangement which I adopted after several trials and modifica- 

 tions in order to meet these conditions was as follows. It consisted of 

 an elongated, round-l^ottomed flask, F, with a long neck ; this flask 

 contained the experimental snlt solution. The moutli of the flask 

 was provided with a cork, through which passed two thermometers, 

 a and h, and a tube .s for tlie escape of steam ; the thermometer a was 

 used to indicate the temperature of the steam, and the thermometer 



