90 
Mr Foster, Estimation of Copper. 
Estimation of Copper. By W. H. Foster, B.A., St John’s 
College. Communicated by Mr H. 0. Jones. 
\Read 26 November 1906.] 
In the Proc. Camb. Phil. Soc. 1902, Vol. xii. Pt. II. p. 97, 
Wood and Berry describe a method of estimating sugar, by 
reduction of copper carbonate (dissolved in a solution of potassium 
carbonate), dissolution of the cuprous oxide formed in ferric 
sulphate solution, and titration of the reduced iron salt by pot. 
permanganate. 
Jones and Carpenter, J.C.S. 1903, Vol. lxxxviii. p. 1394, 
give an account of a method of estimating hydroxylamine which 
is similar in principle to that used by Wood and Berry for the 
estimation of sugar. The investigation described in the following 
paper was undertaken with a view to ascertaining how far either 
of the two methods above referred to might when reversed, be 
applied to the estimation of copper, more especially in the 
presence of other metals. 
By making use of the fact that most metals form readily 
soluble double carbonates with K 2 C0 3 (in presence of KHC0 3 ) 
it seemed that a method of estimating copper in mixtures might 
be devised, which would be of some practical value. 
The method of procedure consists in adding to a definite 
volume of the copper solution to be estimated (which should be 
of a convenient strength), a sufficient quantity of a saturated 
solution of a mixture of potassium carbonate and bi-carbonate, 
in order to produce a solution of the copper potassium carbonate 
which would not decompose on boiling. To this solution, pre- 
ferably when at the boiling point, such a quantity of the reducing 
agent is added as will ensure the complete reduction of the 
copper carbonate to cuprous oxide. The mixture is then heated 
to boiling for about 10 minutes, and filtered rapidly by means of 
the Gooch filter, nearly boiling air free water being used in the 
washing of the cuprous oxide. The precipitate is now quickly 
transferred to a bottle filled with carbon dioxide gas, by means of 
a pointed glass rod, and the portion still adhering to the crucible 
washed into the bottle with a solution of ferric sulphate con- 
taining sulphuric acid. On shaking the bottle which must be 
provided with a stopper ground to fit it, in order that the shaking 
may be done vigorously, the cuprous oxide dissolves, and the 
resulting solution is titrated with standard KMn0 4 solution. 
It will be seen that the method just described is a modification 
of that given in Sutton’s Volumetric Analysis, 7th Edition, p. 175, 
and known as Schwarz’s method. It differs from it, however, in 
that the ferric salt used is the sulphate and not the chloride and 
consequently the reduced salt may be titrated with KMn0 4 
