EDGAR F. SMITH. 22/ 



I have made a number of calculations to obtain cer- 

 tain checks deemed vecy necessary before placing this name 

 at the head of so important an element. I think I can be 

 reasonably satisfied. The analytical ratios here given have 

 been calculated by myself. 



Hibbs' Direct Weighings in Milligrammes. 



No. Salt. 



1 H-39 



2 31.14 



3 38.28 



4 269.70 



5 333-28 



6 512.22 



7 547-62 

 786.90 



9 1106.81 



10 2131.68 



Not reduced to vacuum. 



Below half a gramme of pyroarsenate the results are 

 necessarily of a low apparent precision individually; but 

 collectively, they give the mean 0.66 105 which is only 3 

 high. This corresponds to considerably less than one-tenth 

 of the fall for an increase of o.i in the atomic weight of 

 arsenic. 



Accordingly, these five determinations, in which only 

 from 20 to 500 milligrammes of pyroarsenate were used, give 

 a mean value 75.01 for As, the individual determinations 

 falling almost equally to both sides of this mean. 



The next/br determinations Nos. 6-9, show a systematic 

 error, with a minimum at No. 8. The mean of these four 

 values is 093, or 9 low. This corresponds to one-fourth of 

 the tenth, or to 0.025 high, that is As = 75.025. The amount 

 of pyroarsenate used is from ) to \ grammes, averaging a 

 little over one gramme. 



Finally, we have the last determination, No. 10, in which 

 over 3 grammes of pyroarsenate were used. The analytical 

 ratio is exactly equal to our atomic ratio; hence As = 75, 

 exactly. 



