TIN. 199 



TIN. 



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 SnOj were formed. 



The work done by Mulder and Vlaanderen f 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. 100 

 parts of tin gave of SnO^ : 



127.56— Mulder. 

 127.56 — Vlaanderen. 

 127.43 — Vlaanderen. 



Mean, 127.517, ± .029 



Dumas % oxidized pure tin by nitric acid in a fla.sk of glass. The re- 

 sulting SnOj was strongly ignited, first in the flask and afterwards in 

 platinum. His weighings, reduced to the foregoing standard, give for 

 dioxide from 100 parts of tin the amounts stated in the third column : 



12.443 grm. Sn gave 15.820 grm. SnOj. 127.14 



15.976 " 20.301 " 127.07 



Mean, 127.105, ± .024 



In an investigation later than that previously cited, Vlaanderen § 

 found that when tin was oxidized in glass or porcelain vessels, and the 

 resulting oxide ignited in them, traces of nitric acid were retained. 

 When, on the other hand, the oxide was strongly heated in platinum, 

 the latter was perceptibly attacked, so much so as to render the results 

 uncertain. He therefore, in order to fix the atomic weight of tin, reduced 

 the oxide by heating it in a porcelain boat in a stream of h^^drogen. Two 

 experiments gave Sn = 118.08, and Sn = 118.24. These, when = 16, 

 become, if reduced to the above common standard, 



* Poggend. Annal., 8, 177. 



t Journ. filr Prakt. Chem., 49, 35. iS 



I Ann. Chem. Pharm., 113, 26. 



g Jahresbericht, 1S58, 183. 



