CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



THE TRANSITION TEMPERATURE OF SODIC 



SULPHATE REFERRED ANEW TO THE 



INTERNATIONAL STANDARD. 



By Theodore William Richards and Roger Clark Wells. 



Presented November 12. Received October 22, 1902. 



In a previous paper * it was shown that the transition temperature of 

 sodic sulphate serves as a very well defined fixed point in thermometry. 

 The precautions to be observed in its determination were there stated 

 and a preliminary value was given, referring the transition temperature 

 to the international standard. This value was found by means of 

 two accurately standardized Tonnelot thermometers, Nos. 11142 and 

 11143, kindly loaned by the Jefferson Physical Laboratory; but in order 

 to obtain more certain knowledge of a point so important, obviously 

 more instruments should be used. Furthermore, there was involved 

 an uncertain correction for the column of mercury in the stem, which, 

 owing to the long divisions of the scale, necessarily projected a consider- 

 able distance into the air. From final determinations such uncertainty 

 must be eliminated. 



This i)resent paper describes a number of determinations wholly 

 independent, althougli in excellent confirmation of the older results. 

 These new determinations, in the first place, obviate the uncertain cor- 

 rection for the projecting column. Secondly, by means of three new 

 Baudin thermometers acquired by this Laboratory and recently standard- 

 ized by the International Bureau of Weights and Measures, at .Si'vres, 

 the transition temperature is very accurately referred to the international 

 standard. 



* Am. J. Sci., [I], 6, 201 ; Zeit. pliys. Cliuiii.. 26. 090 (1898). 



