70 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Jour. Chem. B !), 1. 61. .~s.7 



BitZ. Wii-n. Akad , I.IV. (II.), 50. 60. 

 Zeit Anal Clun... VI 1- I 



Jour. Chem. Boc. ^.), VII. 294. 59.1 ? 

 Ber. d. d Chem, Qeaell . II. 692. 



Am. Jour. Bel ,<: Art-, (8, . II 14. 69.2 

 Ann. der Chem., CCXXXIL 821 



Ber. d. d. Chem. GeselL, XXII. n. 



XXII. 891. 



Zeit Anorg. Chem., II. 221. 58.8 



Compt. Rend < XIV. n r.». G0.1 



Zeit. Anorg. Chem., IV. 10. 59.8 



.. 1V ,,.._, 



" VIII. 1. 



" VIII 291. 



" XI. 73. 



" XVI. 8 



" XVIL 236. 



Proc. Amer. Acad., X X X 1 V. 851. 



The present paper. 69.0 



All except four of these investigations were accompanied by similar 

 ones upon tin- atomic weight <<( nickel, ami in general the criticisms made 

 by Richards ami Cnshman in a recent paper upon this Bubject ma\ 

 applied unchanged to the present argument. It is only aecessary to call 

 attention here to the features in which ditl'erences existed. 



The favorite method for the determination of both constants lias been 

 the reduction of the oxides. It is evident from our work upon this 

 method that Russell's cohaltous oxide (1863) must have been contami- 

 nated with a higher oxide; that Ximmermann's material (1886), treated 

 with greater care in more perfect apparatus, was more nearly normal, 

 although still impure; and that Schiitzenberger i 1892) must have driven 

 off some of the oxygen, which should have been weighed, by his employ- 

 ment of a high temperature. It was reserved For Hempel and Thiele 

 (1895) to discover by varying the conditions of work that cohaltous 

 oxide was incapable of giving constant results, although they did not 

 attempt to find the reason of the inconstancy. Their irregular observa- 

 tions were really a proof of the thoroughness and care of their work, 

 while the wonderful constancy of Zimtnermaun's results simply show - a 

 constancy of imperfect conditions. 



The far greater dissociation tension of the higher oxide of nickel makes 

 the method much less dangerous in this case ; hence the similar results 

 for the atomic weight of nickel are both more concordant and more uearly 

 correct thau those for the atomic weight of cobalt. 



