ATOMIC WEIGHTS 



169 



KAuBr^. 



1. SO2 10.64821 



2. SO. 4.71974 



3. H 7.05762 



4. H 4.49558 



5. SO, 8.72302 



6. SO2 7.66932 



7. SO2 7.15498 



8. H 12.26334 



9. H 7.10342 



Mean, 35.461, ± .0028 

 Hence Au = 197.13. 



In five of the foregoing experiments the reductions were effected with 

 sulphurous acid; and in these, after filtering off the gold, the hromine 

 was thrown down and weighed as silver bromide. This, in comparison 

 with the gold, gives the ratio Au : 4AgBr : : 100 : re; 



Au. IjAgBr. Ratio. 



1 3.77753 14.39542 381.080 



2 1.67330 6.37952 381.254 



5 3.09448 11.78993 380.999 



6 2.71860 10.35902 381.042 



7 2.53695 9.66117 380.731 



Mean, 381.021, ± .057 



Hence Au: AgBr: : 100 : 95.255, ±.0142, and Au = 197.16. 

 In the remaining experiments, Fos. 3, 4, 8 and 9, the KAuBr^ was 

 reduced in a stream of hydrogen, the loss of weight, Br^, being noted. 

 In the residue the gold was determined, as noted above, and the KBr 

 was also collected and weighed. The weights were as follows : 



Au. Loss, Br.. KBr. 



3 2.50122 3.04422 1.51090 



4 1.59434 1.93937 .96243 



8 4.34997 5.29316 2.62700 



9 2.51919 3.06534 1.52153 



From these data we obtain two more ratios, viz., Au : Br., : : 100 

 and Au : KBr : : 100 : x, thus : 



Au:Br^. Au:KBr. 



3 121.710 60.405 



4 121.641 60.365 



8 121.683 60.391 



9 121.680 60.398 



Mean, 121.678, ± .0100 Mean. 60.390, ± .0059 



X, 



Hence Au = 197.04, and 197.08. 



