200 THE ATOMIC WEIGHTS. 



127.100 

 127.064 



Mean, 127.082, ±: .012 



Van der Plaats* prepared pure stannic oxide from East Indian tin 



(Banca), and upon the material obtained made two series of experiments 5 



one by reduction and one by oxidation. Tlie results, with vacuum 



weights, are as follows, the ratio between Sn and SnO.^ ap})earing in the 



third column : 



Oxidation Series. 



9.6756 gvm. till gave 12.2967 SnO.^. 127. 091 



12.7356 " 16.18S5 " 127. 114 



23.4211 " 29.7667 " 127.093 



Reduction Series. 



5.5015 grm. SnO.^ gave 4.32S0 tin. 127. 114 



4.9760 " 3.9145 " 127.117 



3.8225 " 3.0078 " 127.086 



2.9935 " 2.3553 " 127.096 



Mean of both series as one, 127.102, ± -0033 



The reductions were effected in a porcelain crucil)le. 



Bongartz and Classen f purified tin by electrol^vsis, and oxidized the 

 electrolytic metal by means of nitric acid. The oxide found was dried 

 over a water-bath, then heated over a weak flame, and finally ignited for 

 several hours in a gas-muffle. Some reduction experiments gave values 

 which were too low. The oxidation series was as follows, with the usual 

 ratio added by me in" a third column : 



Sn. SnO.,. Ratio. 



2.5673 3-2570 126.865 



3.8414 48729 126.852 



7.3321 9-2994 126.831 



5.4367 6.8962 126.845 



7.3321 ^ 9-2994 126.831 



9.8306 12.4785 126.935 



11.2424 14.2665 126.896 



5.5719 7.0685 126.860 



9.8252 12.4713 126.932 



4-3959 5-5795 126.925 



6.3400 8.0440 126.877 



Mean, 126.877, ± .0080 



We now have six series of experiments showing the amount of Sn02 

 formed from 100 parts of tin. To Berzelius' single determination may be 

 assigned the weight of one experiment in Mulder and Vlaanderen's 

 series : 



* Compt. Rend., 100, 52 1S85. 



fBerichte Deutsch. Cheiii. GeselL, 21, 2900. 188S. 



