28 
and magnesium sulphate, were dissolved with an amount of 
copper sulphate, containing (HOI grm. Cu. to 1 litre. Vary- 
ing quantities of this solution were taken, and the copper 
estimated therein with the following results, from which it 
is seen that these salts have no detrimental effect. : — 
Copper found. Copper calculated. 
0-54 mgrm 0-51 mgrm. 
0-71 „ 0-71 „ 
0-91 „ 0-91 „ 
In the same manner the effect of the presence of colour- 
less non-volatile organic matter w T as tested by dissolving up 
13 grins, of sugar with an amount of copper sulphate 
equivalent to 0-0505 grm. copper in 1 litre of water, and the 
copper estimated in two different portions as before, the 
following numbers being obtained : — • 
Copper found. Copper calculated. 
0'52 mgrm 051 mgrm. 
0-82 „ „ 0-81 „ 
In order to see what influence the presence of lead might 
exercise on this method of estimating copper, a quantity of 
the sulphate containing 0 2 55 grm. Cu. was dissolved in 
water, the copper precipitated by potash, washed, and the 
oxide dissolved in nitric acid and the solution after nearly 
neutralizing with ammonia diluted to 1 litre with the ad- 
dition of 2 grm. of lead, nitrate = 1’25 grm. Pb. Vary- 
ing quantities of this solution were taken, and the copper in 
them estimated with the following results : — - 
Copper found. Copper calculated. 
080 mgrm 0'77 mgrm. 
0-75 „ 0-70 „ 
0-51 „ 0-49 „ 
0-49 0-51 „ 
0-38 „ 0-35 „ 
From which it will be seen that lead when present in not 
too large quantity has little or no effect on the accuracy of 
the method. The precipitate obtained on adding potassium 
