46 ATOMIC WEIGHT DETERMINATIONS. 



COBALT. 



The atomic heat of cobalt as determined by Regnault is 

 6.27 if the atomic weight is assumed at 58.8. [Gmelin- 

 Kraut, I. c.) 



E. Rothoff: 68.98(0 = 16); 368.65(0 = 100). 



269.2 parts of cobalt oxide converted into neutral cobalt- 

 ous chloride and precipitated with argentic nitrate gave 

 1029.9 argentic chloride, according to Berzelius' report. 

 {Poqgend. Annal., 5, 1826, 185.) Berzelius recalculates this 

 analysis for CI = 221.64 and Ag = 1.349.66, and gets the 

 value taken. [Berzelius' Lehrbuch, 3, 1220.) 



R. Schneider: 60.006 (0 = 16); 375.04 (0 = 100). 



Determined from four analyses of the oxalate. The car- 

 bon was determined as in organic analysis ; the metal by 

 heating a known weight of the salt first in a current of air, 

 then in oneof oxygen, and by reduction of the oxide in hydro- 

 gen. The mean of the four analyses gave cobalt at 30.003, 

 with an extreme difference of 0.026 for C = 6. The 

 oxalate was prepared by converting the chemically pure 

 cobalt of commerce into roseo-cobaltic cLloride, from which 

 the metal was again reduced, then dissolved in chlorhydric 

 acid and carbonate precipitated, which was digested with 

 oxalic acid. [Poggend. AnnaL, 101, 1857, 398.) 



Marignac objects to this determination that the oxalate, 

 being insoluble, may very likely have retained portions of 

 the carbonate which could not be removed bv washing. 

 {Bibl Univ., Arch, des Sciences, (2,) 1, 1858, 372.)" 



Schneider answers that he obtained nearly identical results 

 from lots prepared at different times, and that he believes 

 that he has convinced himself that the oxalate contained no 

 carbonate. [Poggend. Annal., 107, 1859, 610.) 



Gibbs, reporting Schneider's determination, remarks : 

 " Very numerous and carefully made analyses of the ammo- 

 nium-cobalt bases, executed in my laboratory, indicate 29.5 

 as the true equivalent of cobalt." [Silliman's Amer. Journ., 

 (2,) ^5, 1858, 438.) 



C. Marignac : about 59 (O = 16). 



Five experiments were made on the decomposition of 

 cobalt sulphate by heat. This salt can be readily dried 

 without decomposition, and the acid is completely driven 

 off by heat, but the resulting protoxide contains a slight 



