165 
a yellow color at once develops and the red precipitate flocculates after a 
brief interval. At extreme dilutions where no precipitate forms, a yellow 
tint is observable. This was suspected to be due to colloidal glyoximine 
which should be flocculated by another precipitate, in which case, since 
both silver cyanide and silver cobalticyanide are white, the red nickel 
glyoximine would be readily detectable and the delicacy of the test in- 
creased. The correctness of this view seems to be confirmed by the ex- 
perimental results detailed below. 
EXPERIMENTAL. 
Solutions and Reagents. NiSO, solution, approx. 0.05 molar, from 
Kahlbaum’s ‘“‘Kobalt-frei’’ salt, was standardized by electrolysis (0.05008 
molar) and by precipitation and weighing as nickel glyoximine (0.0496 
molar). The discrepancy is due probably to a trace of iron which was 
detected, the removal of which appeared unnecessary for our purpose. The 
more dilute solutions used were prepared from this by accurate dilution. 
7) Bodlander, Z. anorg. Chem, 39, 227. 
CoSO,, approx. O. 1 molar, was prepared by working up residues from 
cobaltammin salts. Nickel was removed by dimethylglyoxime according 
to the method we have developed and the solution as used gave no evidence 
of nickel by any of the tests applied. Electrolysis showed this solution to 
be 0.0921 molar. Potassium cyanide, 10 per cent. solution. Dimethylgly- 
oxime, 1 per cent. solution in alcohol. Silver nitrate, 1 per cent. solution. 
SENSITIVENESS OF DIMETHYLGLYOXIME AS A REAGENT FOR NICKEL IN 
PRESENCE AND IN ABSENCE OF CYANIDE ION. 
Ten ec. of NiSO, solution of molarity stated in the table below was 
warmed to about 80° and 1 ce. of the reagent added and a drop or two of 
dilute ammonia. To the same volume of each NiSO, solution two or three 
drops of KCN were added. At these high dilutions no precipitate was formed. 
The solution was warmed to 80°, 1 ec. of reagent added and then the AgNO; 
solution dropwise until a permanent white or pink precipitate formed. 
The more concentrated solutions gave at once a pink precipitate; the more 
dilute ones a white precipitate which turned pink on standing. In those so- 
lutions which required more than one hour to form a precipitate the exact 
