The Students' Guide in Quantitative Analysis - Free Ebooks Library

ANALYSIS OF COPPER PYRITES. 39
G, — Estimation of Carbon and Hydrogen.
Ignite one grm. of coal with PbCrO^ in a hard glass
tube 0.25 metre lon^'. Pass the IIjO, CO, and MaSO^
formed through two U-tubes, one containing ignited CaC^,
and the other a solution of Pb(N03)„ and through a potash
bulb, The increase in weight of the first U-tube gives the
IIjO, and that of the potash bulb the COj,
Calculation of Calorific Power. — One part of carbon in
burning yields S.oSo calorific units, and one part of hydrogen
in burning 34,460 calorific units. Hence to calculate total
calorific units in a coal, multiply the percentage of C by
8,080 and divide by 100; also multiply the percentage of
H by 34,460 and divide by ico. Add the quotients.
(A calorific unit is the amount of heat necessary to raise
one grm. of water from 0° to i" C.) See Chem. News,
XXX [V. p. 233. 1876.
Analysis No. 10. — Copper Pyrites.
Determination cf Copper.
Pulverize very finely. Weigh out exactly 2 grms., place
it in a flask of about 300 c.c. capacity and covered with a
small funnel, the stem of which is slipped into the neck of
the flask. Add 20 c.c. cone. HNO3, 5 c.c. cone. HCl, mix-
ing these in flask under the hood. Digest some minutes,
then add cautiously 20 c.c. cone. H;SO^ and boil hard un-
til fumes of HjSO^ appear abundantly. Cool, add water
with caution, dilute not too largely, filter from residue {SiO,,
CaSO,, etc.), and wash. Test residue for copper before
the blow-pipe. Dilute filtrate to 200 c.c. exactly, mix well
by pouring into a dry beaker and back agam three or four
times ;
divide in halves by taking out too c.c. with a pipette