Mr Foster, Estimation of Copper. 
95 
Results : — 
20 c.c. of the solution required 
(1) 34-20 c.c. KMn0 4 sol. (4) 34-40 c.c. KMn0 4 sol. 
(2) 34-70 „ „ (5) 34-30 „ 
(3) 34-40 „ 
20 
1 c.c. KMn0 4 sol. contained — ^ ^ x ’00316 gm. KMn0 4 . 
34-40 c.c. gave 61-80 °/ 0 Cu. 
By gravimetric methods 62-6 °/ 0 Cu (mean). 
The filtering of the precipitate was rather troublesome and 
the time taken for each determination was five or six times that 
required for an estimation in the case of a solution containing 
only copper when grape sugar was employed as reducing agent. 
Under favourable circumstances it would be possible to carry out 
about ten determinations of such a solution in the hour but not 
more than three or four of the solution of German silver. 
Y. Brass. Grape Sugar as Reducing Agent. 
4 gms. copper were dissolved in HN0 3 , sufficient zinc being 
added to make a mixture resembling brass, the whole being made 
up to 500 c.c. 
1 c.c. KMn0 4 sol. = ’00316 gm. KMn0 4 . 
20 c.c. of the solution required amounts of KMn0 4 sol. varying 
from 25’00c.c. to 26T0. Out of eight titrations six gave numbers 
above the theoretical value (25’20 c.c.). 
Phenyl hydrazine as Reducing Agent. 
Since C 6 H S NH. NH 2 when warmed with copper salts is known 
to give cuprous oxide, benzene and nitrogen, it appeared likely 
that it might prove to be a suitable reducing agent for the 
estimation of copper by this method. 
A series of estimations of the mixture resembling brass were 
carried out with the object of ascertaining the behaviour of this 
substance as compared with grape sugar and NH 2 OH. 
The C 6 H 5 NH.NH 2 was used in the form of hydrochloride, 
which was prepared specially for the purpose and used in the 
fresh condition. 
It was found necessary to wash the precipitated Cu 2 0 with 
alcohol, otherwise the solution in the ferric sulphate was turbid 
and the end point consequently not at all easy to determine. 
When washed with alcohol there was no difficulty whatever with 
regard to end point determination, the solution being as clear as 
