174 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



spattering, the salt was heated in a crucible under a layer of fine siliceous 

 sand of known weight. Several crops of crystals of the salt were studied, 

 as a check against impurities, but all gave concordant values. 



Mean, 49.474, ± .0021 



Hence Au = 197.73. 



In his sixth and seventh series Mallet seeks to establish, by direct 

 measurement, the ratio between hydrogen and gold. In their experi- 

 mental details his methods are somewhat elaborate, and only the proc- 

 esses, in the most general way, can be indicated here. First, gold was 

 precipitated electrolytically from a solution of potassium aurocyanide, 

 and its weight was compared with that of the amount of hydrogen simul- 

 taneously liberated in a voltameter by the same current in the same 

 time. The hydrogen was measured, and its weight was then computed 

 from its density. The volumes are given, of course, at 0° and 760 mm. 



These data, with the weight of one litre of hydrogen taken as 0.89873 

 gramme, give the subjoined values in the ratio H : Au ::l:x. 



196.960 

 197.151 

 196.805 



Mean, 196.972, ± .0675 



In the last series of experiments a known quantity of metallic zinc was 

 dissolved in dilute sulphuric acid, and the amount of hydrogen evolved 

 was measured. Tben a solution of pure auric chloride or bromide was 

 treated with a definite weight of the same zinc, and the quantity of gold 

 thrown down was determined. The zinc itself was purified by fractional 

 distillation in a Sprengel vacuum. From these data the ratio 311 : Au 

 was computed by direct comparison of the weight of gold and that of the 

 liberated hydrogen. The results were as follows: 



