The sulphur is thus determined:--Take 1 gram of the coal and mix with
1.5 gram of a mixture of 2 parts of calcined magnesia and 1 part of
carbonate of soda, and heat in a platinum crucible for one hour or until
oxidation is complete. Turn out the mass and extract it with water and
bromine, filter, acidulate with hydrochloric acid, boil off the bromine,
and precipitate with baric chloride (estimating gravimetrically as given
under _Sulphur_). Another method is as follows:--Take 1 gram of the coal
and drop it gradually from a sheet of note paper on to 5 grams of fused
nitre contained in a platinum dish. Extract with water, acidify with
acetic acid, and estimate volumetrically as described under _Sulphur_.
[Illustration: FIG. 73.]
~Calorific Effect of Coals.~--The heat-giving value of a coal is best
expressed in the number of pounds of water, previously heated to the
boiling point, which it will convert into steam. This is generally
termed its evaporative-power. It may be determined by means of the
calorimeter (fig. 73). This consists of a glass cylinder marked to hold
29.010 grains of water. The instrument consists of a perforated copper
stand, provided with a socket and three springs. The socket holds a
copper cylinder which is charged with 30 grains of the dried coal mixed
with 300 grains of a mixture of 3 parts of potassium chlorate and 1 part
of nitre.
Pages:
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768