The Students' Guide in Quantitative Analysis - Free Ebooks Library

DETERMINATION OF TOTAL CARBON. 79
water, then ^vith (a) alcohol, {l>) ether and (c) hot water.
Dry and transfer to flask and determine as in B.
In this process the combined carbon goes off m volatile
hydrocarbons, and graphite +SiO. together with certain
liquid hydrocarbons, remain. The SiO. is removed by the
KHO the hydrocarbons dissolve out in the alcohol and the
ether, \vhUe the latter is removed at last by boiling water.
B -Detsrmmatlon of Total Carbon.
A H. Elliott's modification of Roger's Process. See
Journal of Chemical Society, London, May, 1869; also
Cairns* article in Am. Chem., Vol. 11, p. 140.
_
To 2.5 grms. of borings add 50 ex. of a neutral solution
of CuSO,! containing one part of sulphate to S P^rts of
water; heat gently for 10 minutes; the iron dissolves;
copper is precipitated, and the silica, graphite, and com-
bined carbon remain
:
Fe+CuSO,=Cu+FeSO,.
The cupric sulphate should be as neutral as possible, in
order to avoid loss of combined carbon, in the form of
volatile hydrocarbons, as shown in AA.
Add -o c c CuCl. (I part of chloride to 2 parts of water),
with 50 c.c. strong HCl. and heat for some time nearly to
boiling, until the copper dissolves :
CuCU+Cu=Cu,Cl,.
Prepare an asbestus filter as follows: select a glass tube
of about 3 to 4 cm. diameter, and 1 8 to 20 cm. in ength.
Draw out this tube to taper at one end, and place broken
glass and asbestus, lightly packed, in the narrowed portion
of the tube. (See^r....§ 21S. \ ^' P- 7S90 Filter the
cuprous solution through the asbestus, wash thoroughly