ATOMIC WEIGHTS 29") 



Hence the following values for tin: 



From ratio 2 Sn = 117.971. ± .0258 



" 1 118.18G, ± .0113 



" 3 118.976, ± .0094 



" 4 119.070, ± .0082 



" 6 119.080, ± .087G 



" 5 119.099, ± .0359 



General mean, Sn = 118.648, ± .0052 



The discordance between the first two and tlie last four of these values 

 is glaring, and there seems to be no true compensation of errors. On 

 chemical grounds, the five fairly concordant series of determinations by 

 Bongartz and Classen seem to he better than the earlier measurements. 

 Their arithmetical mean gives Sn = 119.057, which, until further evidence 

 is obtained, should be accepted. New determinations of the atomic 

 weight of tin are much to be desired. 



THORIUM. 



The atomic weight of thorium has been determined from analyses of 

 the sulphate, oxalate, formate and acetate, with widely varying results. 

 The earliest figures are due to Berzelius.' wlio worked with the sulphate, 

 and with the double sulphate of potassium and thorium. The thoria 

 was precipitated by ammonia, and the sulphuric acid was estimated as 

 BaS04. The sulphate gave the following ratios in two experiments. The 

 third column represents the weiglit of ThO.. iiroportioiml to 100 parts of 



BaSO,: 



.6754 grm. ThO, = 1.159 grm. BaSO,. Ratio, 58.274 

 1.0515 " 1.832 " " 57.396 



The double potassium sulphate gave .265 grm. TliO., .156 grm. SO3, 

 and .3435 KoSO^. The SO3, with the Berzelian atomic weights, repre- 

 sents .4537 grm.^BaSO^. Hence 100 BaSO^ is equivalent to 58.408 ThO,. 

 This figin-e, combined with the two previous values for the same ratio, 

 gives a mean of 58.026, ±.214, and Th = 238.9. 



From the ratio between the K.^SO^ and tlie TliO., iu tlie double sul- 

 phate, Th=: 236.88. 



1 Poggend. Annnl., Ki, 3)S. 1S29. Lehrbuch, 3. 1224. 



