2 J. SAKÜT^M: DETETîMTXATTOX OF THE TEMPEILVTÜRE 



the vapour, unless sper'i;il precautions l^e taken, so that the tempera- 

 ture indicated will not be liigher tlian 100°. Tf, on the other hand, 

 the walls of the containing- vessel be maintained at a higher tempera- 

 tiu-e, the thermometer will be exposed to the heat radiated from them, 

 and will indicate a higher temperature. 



For some time past, I have been engaged in an experimental 

 investigation of the determination of the temperature of steam escaping 

 from boiling salt solutions, and have devised a method which is, as 

 far as I can see, free from such objections. V>y tliis means, it can be 

 readily shown that the temperature of the steam escaping from the 

 boiling salt solution is exactly the same as that of the solution itself. 



I'efore proceeding, however, to a description of my own experi- 

 ments, I shall briefly refer to the history of tliis question, discussing 

 the metliods employed and the results obtained by previous workers. 



Historical Summary and Short Critical Review of the Work 



already done. 



Faraday, as long ago as 1822, published the results of his experi- 

 ments upon this question in the Annales de Chimie et de FJujsiquc for 

 that year. Fie found that Avhen the l)ulb of a thermometer was 

 sprinkled over with a salt and then introduced into steam coming out 

 of boiling water, the th(;rmometer showed a temperature higher than 

 100°, especially Avhen it was held horizontally, so as to prevent the 

 salt from ])eing washed awav too quickh'. Still higher temperatures 

 were observed l)y him when, the experiment being otherwise the same, 

 the thermometer l)ulb was wrapped up in a linen or woollen cloth. 

 From these experiments, Faraday concluded that since a salt solution 

 was heated up to its boiling point by the action of steam at 100° 

 upon the salt, therefore the steam generated from a boiling salt solu- 

 tion had only the temperature of 100°. 



