27 
Within moderate limits the amount of potassium ferro- 
cyanide does not affect the accuracy of the method as was 
proved by several experiments, for instance, v/hen Jcc. and 
2cc. of the ferrocyanide were added to the two cylinders re~ 
spectively, water up to the mark, and 5cc. of ammonium 
nitrate to each, then 7cc. of the standard copper solution 
produced in each an equal depth in colour. 
The same may be said of the ammonium nitrate, for in 
one of several trials, all leading to the same result, when 
there were five drops of ferrocyanide in each cylinder, with 
water up to the mark, and 5cc. of ammonium nitrate in one 
and 15cc. in the other, an equal depth of colour was ob- 
tained on running into each 7cc. of the standard copper 
solution. 
The following are the results obtained- by estimating the 
copper in pure solutions of copper sulphate of known 
strength : — 
Copper found. 
Copper calculated. 
205-00 moTm 202-08 
mo-rm. 
32-36 
6-50 
1-18 
1-13 
0-96 
0-75 
0-59 
0-52 
0*42 
0-39 
0-22 
0-13 
0-12 
0-055 
31-32 
6-27 
1-13 
1-21 
1-01 
0-75 
0-61 
0-50 
0-40 
0-38 
0-20 
0-13 
0-10 
0-050 
In order to test the effect which the different salts might 
have on the accuracy of the method, 8-0 grms. of a mixture 
of the following salts, viz. : — Ammonium chloride, sodium 
chloride, potassium nitrate, calcium chloride, calcium sulphate, 
