NICKEL AND COBALT. 305 



ous work as follows, Schulzenberger's measurements of the ratio NiO : Ni 

 being assigned equal weight with those of Mond, Langer, and Quincke : 



Russell 78.593, .0018 



Zimmermann 78.582, .0006 



Mond, Langer, and Quincke 78.545, .0061 



Schutzenberger 78.534, .0061 



Kriiss and Schmidt, reduction series 78.444, .0166 



Kriiss and Schmidt, oxidation series 78.557, zh .0319 



General mean 78-57, db .0006 



In 1889 Winkler * published a short paper concerning the gold method 

 for determining the atomic weights in question, but gave in it no actual 

 measurements. In 1893 f he returned to the problem with a new line 

 of attack, and at the same time he takes occasion to criticise Kriiss and 

 Schmidt somewhat severely. He utterly rejects the notion that either 

 nickel or cobalt contain any hitherto unknown element, and ascribes the 

 peculiar results obtained by Kriiss and Schmidt to impurities derived 

 from the glass apparatus used in their experiments. For his own part 

 he now works with pure nickel and cobalt precipitated electrolytically 

 upon platinum, and avoids the use of glass or porcelain vessels so far 

 as possible. With material thus obtained he operates by two distinct 

 but closely related methods, both starting with the metal, nickel or 

 cobalt, converting it next into neutral chloride, and then measuring the 

 chloride gravimetrically in one process, volumetrically in the other. 



After precipitation in a platinum dish, the nickel or cobalt is washed 

 with water, rinsed with alcohol and ether, and then weighed. It is next 

 dissolved in pure hydrochloric acid, properly diluted, and by evapora- 

 tion to dryness and long heating to 150 converted into anhydrous chlo- 

 ride. The nickel chloride thus obtained dissolves perfectly in water, 

 but the cobalt salt always gave a slight residue in which the metal was 

 electrolytically determined and allowed for. In the redissolved chloride, 

 by precipitation with silver nitrate, silver chloride is obtained, giving a 

 direct ratio between that compound and the nickel or cobalt originally 

 taken. The gravimetric data are as follows, with the metal equivalent 

 to 100 parts of silver chloride given in a final column : 



Nickel 



* Ber. Deutsch. Chem. Gesell., 22, 891. 

 fZeit. Anorg. Chem., 4, 10. 1893. 

 20 



