106 JOURNAL OF THE 



2d. The distance between the atomic weights renders them 

 easy to memorize and is more convenient for the illustration of 

 the Periodic Law. 



3d. About two-thirds of the atomic weights are either whole 

 numbers or vary from whole numbers bv fractions of^-or less. 



4th. The adoption of this as a unit practically means the re- 

 tention of most of the numbers so long in use. The valuable 

 literature of the past three or four decades need not be rendered 

 less useful and intelligible to the chemists of the present and 

 the future, as it would be by radical changes in these combining 

 numbers. 



Some chemists seem to feel an especial repugnance to this unit 

 because it is too arbitrary and unusual, not bearing upon its face 

 the fact that it is the unit, and again because hydrogen is then 

 represented by the number 1.0025. The arbitrariness of it seems 

 unavoidable: as to why they should be troubled by the number 

 given hydrogen is not very apparent. The fraction is an easy 

 one to handle and may often be neglected. It can make no pos- 

 sible difference in the close calculations of organic chemistry 

 cited by Meyer and Seubert, whether H=l and 0= 15.96 or 

 H= 1.0025 and 0=16. The only thing is to keep the ratio 

 which most exact research reveals as existing between the two. 

 The tendency of the day is toward 0=16 and it should be 

 universally adopted. To avoid dangerous assumptions the other 

 atomic weights should be rigidly put down in accord with the 

 most accurate determinations available. This brings us to con- 

 sider another difficulty and cause of variation. 



METHODS OF CALCULATION. 



Clarke, Sebelien, and others, who have worked over this 

 problem, have been greatly troubled as to what data should be 

 used in the recalculations and what rejected. Manifestly the 

 results of many of the older experimenters can lay no great 

 claims to accuracy. Some, as Clarke says, are " chemically 

 worthless because of constant errors." Many have neglected 

 proper precautions or necessary corrections. And yet there are 



