290 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Hence, 



From ratio 3 Zr = 90.030, ± .2390 



" 1 90.374, ± .0201 



" 6 90.677, ± .0138 



" 2 90.790, ± .0804 



" 5 90.805, ± .0297 



" 4 91.538, ± .4350 



General mean, Zr = 90.621, ± .0105 



The final combination, in this case, is unsatisfactory because of the 

 wide divergence among tlie individual values. On chemical grounds, 

 ratios 1 and 5 seem to be the only ones worth considering. Their weighted 

 combination gives Zr= 90.-183. The value adopted in the latest Interna- 

 tional table is 90.(!. The atomic weight of zirconium evidently needs 

 careful revision. 



Tm. 



The atomic weight of tin has been determined by means of the oxide, 

 the chloride, the bromide, the sulphide and the stannichlorides of potas- 

 sium and ammonium. 



The composition of stannic oxide has been fixed in two ways: by 

 synthesis from the metal and by reduction in hydrogen. For the first 

 method we may consider the work of Berzelius, Mulder and Vlaanderen. 

 Dumas. Van der Plaats and Bongartz and Classen. 



Berzelius ' oxidized 100 parts of tin by nitric acid, and found that 

 127.2 parts of SnO, were formed. Hence Sn = 117.6-"). 



The work done by Mulder and Vlaanderen ' was done in connection 

 with a long investigation into the composition of Banca tin, which was 

 found to be almost absolutely pure. For the atomic weight determina- 

 tions, however, really pure tin was taken prepared from pure tin oxide. 

 This metal was oxidized by nitric acid, with the following results. One 

 hundred parts of tin gave of SnOj : 



127.56— Mulder 

 127.56— Vlaanderen 

 127.43 — Vlaanderen 



Mean. 127.517, ± .029 



Hence Sn=i 116.3. 



' Poggend. .Annal., 8, 177. 



^'Joiiiii. prakt. Chem., 49, 35. ISW. 



