520 v Day and Sos?nan — Nitrogen Thermometer Scale 



The vessel which contained the nitrates consisted of a cylin- 

 drical wrought iron tank 152 mm in inside diameter and of T mm 

 wall thickness, into which the bottom plate was welded with an 

 oxy-acetylene flame. This detail is perhaps worth some em- 

 phasis, because it was the only tank of three which were made 

 up with various joints in the bottom which proved able to hold 

 the nitrates up to a temperature of 630° without leaking. 



Fig. 1. 



Fig. 2. 



THERMO-ELEMENT 



THERMO-ELEMENT 



Fig. 1. Nitrogen- thermometer bulb in double nitrate bath. (The two 

 thermoelements on the outside of the bulb are not shown.) 



Fig. 2. Apparatus for the determination of the melting point of zinc in 

 the nitrogen thermometer nitrate bath. 



Scale : 1 to 6-5. 



As at first used this tank was merely a covered vessel with- 

 out partitions into which a turbine stirrer, operated by an elec- 

 tric motor, was inserted. The comparatively loose lower bearing 

 of the turbine was lubricated by the liquid itself, the upper one 

 was water-cooled. Alongside of this stirrer, and 30 mm distant 

 from it in the bath, was the bulb of the gas thermometer. 

 Although the stirring in the tank was vigorous, temperature 

 differences amounting to 0*4° appeared between the top and the 

 bottom of the bulb at 400°. The current in the liquid was up- 



