64 Contributions to Chemistry from the 
means of nitrite of potassium, but it is at least very much mote” 
convenient and requires much less time. The complete preci 
tation of cobalt in the form of Co,0,,2NO,+3KONO, usual 
requires at least forty-eight hours, and rarely succeeds perfectly 
except in experienced hands. : 
§ 5. 
cution are concerned. e method labors, however, under 4 
single disadvantage : the introduction of zinc renders it difficwl, 
or at least inconvenient, to determine with accuracy other 
ments which may be present with the copper. It has occu 
to me that this difficulty might be overcome, the principle of th 
method being still retained, by precipitating the copper by ele 
trolysis with a separate rheomotor. The following numerical 
results, which are due to Mr. E. V. M’Candless, will satisfact 
rily show the advantages of the method for the particular case 
Number. Copper found. 
I. 1:2375 0°3145 
a. 0°4235 071075 
a: 1°:0640 02705 
Iv. 1:3580 0°3440 
‘A 0°5665 0°1450 
A, 0°4735 071205 
