The Students' Guide in Quantitative Analysis - Free Ebooks Library

30
QUANTITATIVE ANALYSIS.
with boiling water, and transfer contents of filter to a flask
holdiiitr about 200 c.c.
In making this transfer, the carbon,
asbestus, and broken glass may be blown into the flask
too'ether, in order to use as little water as possible. Add
to the contents of the flask about 3 grms. of CrOj, (or if
this is not available, about 5 grras. KXr^Oj), and arrange
apparatus as in the determination of COi by direct weight,
Ami/sis No, 7, note 8, II (page 34}. Avoid adding more
water than absolutely necessary to transfer the carbon.
Add 30 c.c. to 40 c.c. concentrated H^SO^, little by little,
shaking constantly, and closing cock of funnel-tube each
time. Finally, heat gently to boiling, not allowing more
than three bubbles of CO^ gas to pass per second
3C+4Cr034-6H,SO,=:3CO,-h2Cr,(SO,),-|-6H,O.
Boil one minute, attach guard tube of soda lime, and
aspirate slowly, three bubbles per second. Weigh the
soda-lime tube for amount of CO^. absorbed, and calculate
the amount of carbon.
Note~~Tht carbon separated from cast-iron by treatment
with .sulphate of copper contains H and O, and cannot
therefore be determined by weighing directly. Schutzen-
bcrgcr and Bourgeois assig.T to it the composition expressed
by the formula C„3H,0, and consider it related to graphitic
acid. BulleHn de la SocUtk Ckimiqiie dc Paris, Vol, 23.
No. 9.
EB.-Other Methods for determining Total Carbon.
mJ^i.^Tl?"'^,^'' °^ "'^^^^'^^ '^^^e been devised for deter-
rcmarki .'' "' '°'"" °^ ^^"^'^h
ema ^^ *i» briefly outline,
kmg. however, that the foregoing is entirely satii.
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