170 
These results indicate that this method is not very sensitive and fails 
when much cobalt is present. 
C. Tue Liesic-GatuHE Meruop. 
10 ce. portions of CoSO., 0.0921 molar, with varying amounts of NiSOs 
were treated with a slight excess of KCN over that required to dissolve the 
precipitate, and heated and rotated until complete oxidation of the cobalto- 
cyanide had taken place. They were then diluted to 50 ce. and freshly pre- 
pared sodium hypobromite added. After the precipitate had flocculated, 
it was filtered off, washed, dissolved in dilute HCl, neutralized with ammonia 
and tested for Ni with dimethylglyoxime. Results below. 
TABLE VIII. 
| 
NiSO; 
0.C€005 molar Mg. Ni. | Ratio Ni : Co |Ratio Ni : H2O| Results. 
CC. aetna a On 2A T 12/206 Blk. ppt. Ni confirmed 
GLCChamelias Sraareet .1760 | 1 : 309 Blk. ppt. Ni confirmed 
ER ey ae ie oe Fil 72 1 : 462 Blk. ppt. Ni confirmed 
Ss CA A ee .O880 ag 1 : 568,000 Blk. ppt. Ni confirmed 
AR Ce eee nee ae ee -0587 | | 1°: 925 1 : 852,000 Blk. ppt. No Ni 
INCE ea wee See .0293 / 1 : 1850 Blk. ppt. No Ni 
WONGS 2 tes see | None Blk. ppt. No Ni 
This method is shown to be capable of detecting 0.1 mg. nickel in a volume 
of 50 ce., Lut a confirmatory test must in every case be applied as the ppt. 
contains Co(OH)s. 
Comparing the results of the three methods, the minimum amount of 
nickel detectable within one hour in a volume of 50 ce. is found to be: 
Siwereory.. 13.28 # Shen Coenen ane cea 0.02 mg. 
Pachupacy- bresiwell> so .5.% |. < Shee ne de ae ee .23 mg. 
DAE DAP- ATG, 55.0 oP eek ns eee ce ee .O9 mg. 
These figures do not adequately convey the relative merits of the three 
. methods, for it should be noted in addition that the Liebig method requires 
a confirmatory test to make the result trustworthy; the Treadwell method 
failed to show the stated minimum amount of nickel when so little as 231 
times as much cobalt as nickel was present, while the silver method appears 
