RICHARDS. — TRANSITION TEMPERATURES OF SODIUM CHROMATE. 183 



The Beckmann thermometer in this mixture indicated 0-580°. Upon 

 crystallizing the material once more, and separating the mother liquor 

 by centrifugal action, the crystals still gave exactly the same transition 

 point, 0.580°, — the atmospheric pressure having remained essentially 

 constant. Therefore it was clear that the material was as pure as it 

 could be obtained by crystallization, and the final estimation was 

 made. 



The individual readings were corrected for stem exposure, and all 

 averaged to give the observed value used in calculating the tempera- 

 ture referred to the hydrogen scale. The ice-points, which are the 

 most uncertain part of this determination, were taken as the averages 

 of four separate fairly concordant sets of readings, two of which were 

 made some time before the determinations, and two immediately after- 

 wards. As the thermometers are old and well seasoned, this procedure 

 seemed likely to furnish the best result. 



Thermometer 15200, 



Reading in salt (cor.) 19.804° In ice + .201° 



Correction, calibration 



" internal pressure 



Corrected reading in ice 



Correction, fundamental int. 



Correction to hydrogen scale 



Thermometer 15276 

 Reading in salt (cor.) 

 Cor. calibration 

 " internal pressure 



Corrected reading in ice 



Cor. fundamental interval 



Cor. to hydrogen scale 



Total average of two final readings 



The average of the two preliminary readings was 19.522° -f .004^, 

 a result as near as could be expected to the final value, considering the 



