AXEL ERDMANN. 277 



The work of Axel Erdmann was undertaken at the 

 request of Berzelius, and reported by him to the Swedish 

 Academy, and in his Annual Report, March 31, 1844, 

 (French Series, transl. Plantamour, No. 5, p. 71; Paris, 

 1845). He found it necessary to use porcelain crucibles. 



The entire range is only equivalent to o.i on the atomic 

 weight, while the analytical excess of the mean represents 

 only 0.05 high. Crucible work in those days was quite dif- 

 ferent from what it is now. 



From all I can tell, by looking carefully over the entire 

 mass of work done, I must conclude this to be the true 

 value. 



The determinations made since 1844 have been very 

 numerous, especially in more recent years. 



We have even a goodly number of determinations by 

 students, called " practice work of students;" but such work 

 should remain sacred to the laboratory, and not be published 

 as atomic weight determinations (under Morse and Keiser, 

 in Johns Hopkins University, Baltimore, containing 51 

 determinations; see Clarke, p. 150, who puts the mean in 

 his Olla Podrida, of course). 



All determinations by means of hydrogen must, at pres- 

 ent, be ruled out, because of the uncertainty affecting the 

 latter. This excludes Van der Plaats, 1887, Mallet, 1890; and 

 the student's work. 



Of the wet way processes, we must note the most preten- 

 tious by Richards and Rogers, of Harvard University, which 

 point to 65.5 as the atomic weight of Zinc. We calculate for 

 this value 65.5: 



Zn Br2 : 2 Ag 225.5 : 216=1.04 398. Chg. 46 high. 

 Series A No Ag determination. 



" B 4 Det., 411 376535. Mean 6 low. 



" C 3 Det., 380 377; 3. " 19 low. 



Zn Br2 : 2 Ag Br=225-5 : 376 = 0.59 973. Chg. 26 high. 

 Series A 5 Det., 984 961; 23. Mean 2 high. 



" B 4 Det., 977 959; 18. " 6 low. 



" D 3 Det., 962 961 ; i. " 12 low. 



Richards sacrifices everything to concordance, as well 

 known, and specially striking in the present work. In the 



