150 ILLINOIS ACADEMY OF SCIENCE 



the crystals into a second flask from which more of the water 

 was evaporated and the process of crystallization repeated. 

 By adding small quantities of water to the first flask and 

 then pouring the soluble portion from each flask into the next 

 in the series, the material was split into fractions of different 

 solubilities. By continuing this method of fractional crys- 

 tallization for a period of about two years distinct colors 

 were seen in portions of the series, indicating a partial sepa- 

 ration of the elements which were present in the original 

 mixture. 



Portions of such a series which showed similar properties 

 were set out and the material further fractionated by adding 

 a precipitant in small quantities. After each addition the 

 precipitate was removed, and in this manner several frac- 

 tions were obtained with varying degrees of basicity. The 

 precipitants used in this work were K 2 Cr0 4 , NH 4 OH and 

 NaN0 2 . The effect of the treatment was followed by ob- 

 serving the changes in the lines of the absorption spectrum 

 and by using trial methods for determining the atomic 

 weights. 



The best yttrium material obtained contains only traces of 

 erbium and holmium. The final determination of the atomic 

 weight is being made in the following manner: A quantity 

 of pure yttrium oxide is placed in a double-necked quartz 

 flask and its weight determined. This is then dissolved in 

 pure HC1 and the flask is attached to a drying train through 

 which dry air is passed until the solution in the flask crystal- 

 lizes. Then the temperature of the flask is gradually raised 

 while dry nitrogen and dry HC1 are successively passed through 

 the flask until the chloride is thoroughly dehydrated. Finally 

 the anhydrous chloride is fused in an atmosphere of HC1. 



The results so far obtained indicate that the atomic weight 

 of yttrium is somewhere between 88.5 and 89. 



