with Boiling Point of Sulphur. 519 



temperatures. The gas thermometer measurements were made 

 in a liquid bath, using a sensitive resistance thermometer to 

 transfer the temperature from the bath containing the gas 

 thermometer bulb to the (independent) sulphur boiling point 

 apparatus. The lower temperatures were then interpolated by 

 means of the platinum resistance thermometer. The new 

 determinations were published so recently that there has been 

 no opportunity for confirmation by other experimenters, but 

 they appear to be free from any error greater than one or two 

 tenths of a degree, and therefore indicate a very considerable 

 increase in the accuracy of the results when compared with the 

 earlier (1900) scale which is now in general use. Holborn 

 and Henning's new results, on the thermodynamic scale, are in 

 part as follows : 



Benzophenone (boiling point) 305-89° 



Cadmium (melting point) . 320*92 



Zinc " " -_. 419-40 



Sulphur (boiling point) 444-51 



In certain studies* now under way in this laboratory on the 

 effect of pressure upon equilibria greater accuracy is now 

 required in the measurement of these particular temperatures 

 than had previously been necessary. We therefore determined 

 to repeat these measurements, with more elaborate precautions 

 to secure a uniform temperature about the bulb, this being, as 

 stated above, the one factor in our measurements about which 

 some uncertainty remained. At any rate it was important to 

 establish the identity and the magnitude of the error in the 

 earlier measurements which may have been due to this cause. 



2. Apparatus. 



JSTo attempt will be made to describe in detail the gas 

 thermometer and accessories used in this investigation. A full 

 description of the apparatus, with illustrations, will be found 

 in the publications to which reference has been made. No 

 change whatever was made in the gas thermometer system for 

 these measurements, except for the substitution, about the 

 bulb, of a liquid bath, made up from potassium and sodium 

 nitrates in eutectic proportions (55 per cent KN0 3 , 45 per cent 

 NaN0 3 ). This bath was introduced into the furnace bomb 

 described in connection with the earlier apparatus in place of 

 the platinum wire furnace previously used. The insulating 

 material was dried magnesia powder, as heretofore, and the 

 bomb was water-jacketed throughout to protect the manometer. 

 The general appearance of the furnace is shown by the accom- 

 panying diagram (fig. 1). 



* Johnston and Adams, this Journal, xxxi, 501-517, 1911. 



