412 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



After the salt had been dried, a carefully weighed U-tube containing 

 resublimed phosphorus pentoxide was attached to the end of the tube. 

 This U-tube was provided with ground glass stopcocks lubricated with 

 Ramsay desiccator grease. The silver chromate was gradually heated 

 until fusion took place, and a slow current of air was allowed to pass 

 through the system for one half hour in order to make certain that all 

 moisture was carried into the absorption tube. Finally the phosphorus 

 pentoxide tube was reweighed. 



The pentoxide tube was weighed by substitution with the use of a 

 counterpoise of the same size and weight. Before being weighed both 

 tubes were carefully wiped with a damp cloth and were allowed to 

 stand near the balance case for thirty minutes. Care was taken to 

 equalize the pressure inside and outside the tubes by opening one stop- 

 cock immediately before hanging on the balance. 



In order to test the efficiency of the drying apparatus, blank ex- 

 periments were carried out by allowing a slow current of air to pass 

 through the apparatus into the weighed pentoxide tube. The varia- 



