THEODORE WILLIAM RICHARDS BAXTER 741 



the nearest approach to perfection which had ever been attained. 

 Constant study of Stas's work enabled Kichards to improve upon 

 the former's methods in many ways, without, however, at first arous- 

 ing any susj)icion of inaccuracy in Stas's experiments. For the most 

 part the work of the two had not overlapped, and there had been 

 insufficient basis for comparison. But ultimately discrepancies be- 

 gan to appear, and in 1904 a redetermination of the atomic weights 

 of sodium and chlorine was completed which showed conclusively 

 that in the case of these elements Stas's work was vitiated by appreci- 

 able errors not difficult to trace. Subsequent developments in Rich- 

 ards's laboratory have shown that Stas, although years ahead of his 

 time, was in error by important amounts in nearly all his work. 

 A new era in analytical accuracy was thus inaugurated by Richards 

 and the students who worked under him. 



Later, in 1913, when the question was raised of probable differences 

 between the atomic weight of common lead and those of isotopes of 

 radioactive origin, it was to Richards's laboratory that Dr. Max 

 Lembert was sent from Karlsruhe with specimens of uranium lead in 

 order to settle this important question. The first direct evidence of 

 the lower atomic weight of uranium lead resulted from their 

 investigation. 



Richards is most widely known for his work on atomic weights. 

 It was this work which brought him membership in the American 

 Academy of Arts and Sciences at the age of 23 and in the National 

 Academy of Sciences at the age of 31, as well as the Nobel prize at 

 47. From 1899 to 1902 he was a member of the International Com- 

 mittee on Atomic Weights and since 1919 of the International Com- 

 mittee on Elements and the subcommittee on atomic weights. He 

 never lost interest in this field, and there has seldom been a time 

 when the investigation of one or more atomic weights has not been 

 under way in his laboratory. Furthermore, the experience in exact 

 methods thus obtained was invaluable in the quantitative develop- 

 ment of other fields in which he ultimately became interested. 



While Richards's original contributions in fields of physical chemis- 

 try other than that of atomic weights are too numerous and varied 

 to be described in detail here, certain phases of the work should be 

 emphasized because they represent steps in advance as important 

 from the standpoint of precision as his determinations of atomic 

 weights. His first published paper was concerned with a minor prob- 

 lem in thermochemistry, the constant heat of precipitation of silver 

 chloride. Later, recognizing that this portion of the field of thermo- 

 dynamics was of fundamental importance, he devoted much time and 

 energy to its practical and theoretical aspects. From a practical 

 point of view he endeavored very successfully to increase the accu- 

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