164 THE ATOMIC WEIGHTS. 



From KCl : Au ratio Au ^ 196.186, ± .101 



From Hg : Au ratio " = 196. 113, dz -335 



From P : Au ratio '• = 195.303, ± .589 



From BaSO^ : Au ratio " = 195.794, =h 1-234 



General mean " = 196.155, i .095 



Or, if = 16, Au = 196.606. 



As gold is a metal which can be readily applied to the 

 determination of the atomic weights of other elements, an 

 experimental revision of its atomic weight is very desirable. 



NICKEL AND COBALT. 



On account of the close similarity of these metals to each 

 other, their atomic weights, approximately if not actually 

 identical, have received of late years much attention. 



The first determinations, and the only ones up to 1852, 

 were made by RothhofF; * each with but a single experi- 

 ment. For nickel 188 parts of the monoxide were dissolved 

 in hydrochloric acid ; the solution was evaporated to dry- 

 ness, the residue was dissolved in water, and precipitated 

 by silver nitrate. 718.2 parts of silver chloride were thus 

 formed ; whence Ni = 58.925. The same process was applied 

 also to cobalt, 269.2 parts of the oxide being found equiva- 

 lent to 1029.9 of AgCl. Hence Co = 58.817. These values 

 are so nearly equal that their differences were naturally 

 ascribable to experimental errors. They are, however, en- 

 titled to no special weight at present, since it cannot be 

 certain from any evidence recorded that the oxide of either 

 metal was absolutely free from traces of 'the other. 



In 1852 Erdmann and Marchandf published some re- 

 sults, but without details, concerning the atomic weight of 

 nickel. They reduced the oxide by heating in a current of 



* Cited by Berzelius. Poggend. Annal., 8, 184. 1826. 

 f Journ. fur Prakt. Chem., 55, 202. 1852. 



