RICHARDS. — A TABLE OF ATOMIC WEIGHTS. 295 



vsalized by eager investigators, who seek to make up for a possible lack 

 of quality by a superabundance of quantity. "A single determination, 

 well worked out, is better than twenty incomplete ones. Too much can- 

 not be said against the multiplication of incomplete or carelessly ob- 

 tained data ; for such data carry with them not only uncertainty and 

 confusion in the present, but also additional labor for a reviser in the 

 future." * Every reaction must be assumed to involve some constant 

 error, and every substance must be assumed to contain some constant 

 impurity, until a proof of the contrary is obtained. Our wofuUy discordant 

 data furnish a heavy presumption against almost any chemical method, 

 when greater accuracy than one part in four or five hundred is desired. 



The standard = 16.000 is adopted below, as likely to be the most 

 convenient for many years to corae.| The last figure of each number 

 given in the following table cannot be considered in any case certain. 

 It is often probably not much more than one unit in error ; although the 

 uncertainty may amount to as much as six or eight units in some cases. 

 Of course the decimal notation does not admit of closer indications without 

 an individual explanation in each case. For example : iron, germanium, 

 and gallium are given in the table as 56.0, 70.0, and 72.5 respectively. 

 The first is probably known within 0.1 or 0.2, while the other two 

 may easily be 0.5 in error ; but the method of expressing the results 

 does not admit of this grade of distinction. 



The aim has been to construct a convenient working table, which 

 shall carry with it all that is trustworthy, and nothing that is unneces- 

 sary. It is almost needless to state that the well known standard works 

 of Clarke, Meyer and Seubert, Ostwald, Van der Plaats, and others, 

 have been freely consulted in the preparation of this table, as well as 

 many of the original papers. 



Especially am I indebted to Professor Clarke for his last gigantic 

 collection of data and results, J which would have made the present table 

 a work of supererogation, if he had viewed the subject from a somewhat 

 less mathematical standpoint. Professor Clarke's method of decision 

 places the credit with the skilful manipulator ; I have striven to give 

 the thoughtful chemist who is not so clever with his hands the credit 

 which I think belongs to him. Tlie fact that the two tables usually 

 agree is due either to the best method's having fallen into the best hands ; 

 or to Professor Clarke's having wisely forsaken the rigid application of his 



* These Proceedings, XXXI. 99 ; XXVI. 294. 



t Compare F. W. Kiister, Zeit. Anorg. Chem., XIV. 251. 



t Smithson. Misc. Coll., Constants of Nature, V. (1897.) 



