336 CARNEGIE INSTITUTION OF WASHINGTON. 



tional Grignard treatment of various samples of lead has been begun 

 and is being prosecuted systematically. The process has not pro- 

 gressed far enough to settle the question. Mr. King's salary has been 

 paid from another source, but he is employing apparatus belonging to 

 the Carnegie Institution of Washington. 



(4) Atomic Weight of Rubidium. 



Miss Edith H. Lanman, a graduate student of Radcliffe College, 

 undertook the study of the atomic weight of rubidium with the idea of 

 preparing purer material than has thus far been used and of clearing 

 up a discrepancy in the details of earlier work. She conducted an 

 elaborate series of fractional crystallizations of rubidium dichlorio- 

 dide, testing spectroscopically the march of impurities. In this way a 

 considerable quantity of very pure rubidium dichloriodide is at hand, 

 almost ready for the determination of the atomic weight next year. 



(5) Purification of Gallium by Fractional Crystallization and Effect op 

 Pressure upon the jMelting-Point. 



Mr. S. Boyer, who had previously tested the purification of gallium 

 by electrolysis as M^ell as by heating in a vacuum, found that one of the 

 best methods of getting rid of small residual traces of impurity was by 

 the fractional crystallization of the metal. In this way he was able to 

 prepare a sample of gallium having a constant melting-point. After 

 all corrections had been applied, this purest specimen was found to 

 melt at 29.752° on the international hydrogen scale. Mr. Boyer then 

 determined the effect of pressure on this melting-point by applying 

 pressure to a quantity of half-melted crystals in a Richards piezometer 

 confined in a steel cylinder (kept at a temperature somewhat below the 

 melting-point) until equilibrium was attained. An increase of 300 

 megabars pressure was found to cause a lowering of the melting-point 

 of 0.612°. The volume decrease being 3.13 per cent (or 0.00537c. c.per 

 gram) from the familiar equation of Clapeyron the latent heat of 

 melting is thus found to be 19.04 calories per gram. 



(6) Surface Tension of Liquid Gallium. 



The work on surface tension mentioned last year was continued by 

 Mr. Boyer with even greater precautions. A special study was made 

 of the size of drop necessary in order to give the true maximum result. 

 The values for mercury and gallium (respectively, 44.06 and 36.55) 

 were essentially equal to those found in the earlier investigation. 



(7) Study of Thallium Amalgams. 



Mr. Charles P. Smyth continued his study of thalhum amalgams 

 containing less than 20 per cent of mercury. He obtained definite 

 evidence that the potential of amalgamated thallium is different from 

 that of pure thallium, due to the formation of a solid solution which 

 contains as much as 12 per cent of mercury. He studied the properties 



