108

QUANTITATIVE AGIUCi'LTl-RAL ASALYMX

(a) begun and finished below room temperature, (b) begun below
and finished above or (c) begun and finished above. These
types are illustrated in Fig. 29. The relative slopes of the ends
of the curves represent R\ and R».
It will be observed that these slopes are easily determined in
curve (6) but that it is especially difficult to decide an to what
temperature should be taken as the maximum produced by the
fuel combustion, in the experiment represented by curve (a).
Conditions represented by curve (6) are to be obtained when
possible.

time
i<'hj. 29.— Time-tarn jK'ruUm* cur von.
Determination of Heat of Combustion of Fuels, Foods or Feeds,*—Place
the lower half of the bomb in the holder and the fuel pan in the, wire support,
after having wired the fuse wire according to Fig, 2H.
Extend the wire across the pan, allowing it to dip Mifltekmtiy to be in
contact with the substance, which is later to he placed in the pan. The wire
must in no ease touch the pan. The fune wire Hhould be phwcd in series
with two 100-watt. lamps in parallel when the 110-volt power circuit w used
for firing.
The material whose calorific value in to be determined should be ground
to pass a GO-mesh sieve and it should be dried at HX>" before, weighing the
sample for combustion. If the material is a liquid, wich uk milk, or a sub-