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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



.829 grm. P precipitated 8.714 grm. Au. 1051.15 



.754 " 7.930 " 1051.73 



Mean, 1051.44, ± .196 



Hence, if P = 31, Au = 195.568. 



Levol's ' estimation of the atomic weight under consideration can 

 hardly have much value. A weighed quantity of gold was converted in 

 a flask into AuCl.,. This was reduced by a stream of sulphur dioxide, 

 and the resulting sulphuric acid was determined as BaS04. One gramme 

 of gold gave 1.782 grm. BaSO,. Hence Au = 196.49. 



All these values may be neglected as worthless, except that derived 

 from Berzelius' KoAuCl,; series. 



In 1886 Kriiss " published the first of the recent determinations of the 

 atomic weight under consideration, several distinct methods being re- 

 corded. First, in a solution of pure auric chloride the gold was pre- 

 cipitated by means of aqueous sulphurous acid. In the filtrate from the 

 gold the chlorine was thrown down as silver chloride, and thus the ratio 

 Au : 3AgCl was measured. I subjoin Kriiss' weights, together with a 

 third column giving the gold equivalent to 100 parts of silver chloride: 



Au. 



7.72076 

 5.68290 

 3.24773 

 4.49167 

 3.47949 

 3.26836 

 5.16181 

 4.86044 



Mean, 45.824, ± .0020 



Hence Au = 197.05. 



The remainder of Kriiss' determinations were made with potassium 

 auribromide, KAuBr^, and with this salt several ratios were measured. 

 The salt was prepared from pure materials, repeatedly recrystallized 

 under precautions to exclude access of atmospheric dust, and dried over 

 phosphorus pentoxide. First, its percentage of gold was determined, 

 sometimes by reduction with sulphurous acid, sometimes by heating in 

 a stream of hydrogen. For this ratio, the weights and percentages are 

 as follows, the experiments being numbered for further reference, and 

 the reducing agent being indicated : 



' Untersuchungen iiber das Atomgewicht des Goldes. Miinchen, 1886. 112 pp., Svo. 

 ^'Ann. Chim. Phys. (3), 30, 355. 1850. 



