The Students' Guide in Quantitative Analysis - Free Ebooks Library

I06
qUANTITATIVK ANALYSIS.
article ; it should be heated in a porcelain dish to expel
water and ammonia before using.
Operation : Fill the combustion tube about one-third ful)
of warm soda-lime and let it cool ; then
mix this in an
agate mortar with 0.2 to 0.4 grms. of the dry ferrocyanide
of potassium, and introduce the mixture again into the
tube ; rinse the mortar with a little soda-lime, and then
fi!l the tube with the same nearly to the open end. Insert
a small plug of asbestos loosely, attach the absorption bulb
containing; the sulphuric acid by a well-fitting cork, and
place the tube in the combustion furnace. Begin to heat
the tube at the end nearest the cork, and proceed gradu-
ally towards the other ^nd.
The gas evolved should bubble quietly through the ab-
sorption tube, and when it ceases to pass break the tail-
piece of the combustion tube, and aspirate gently through
the whole apparatus.
Detach the absorption tube, empty its contents into a
beaker, rinse well, add a little litmus, or cochineal solu-
tion, and determine, by means of normal KHO, the
amount of acid remaining imneutralized by the ammonia.
For details of this process see Analysis No. 12,
Theoretical Camposition of Potassitim Ferrocyanide,
N
f;::
T.
,^
3H.O
* '7-^
-^^-^
^3-3
• • • 37.0
J^^
100.0