Tgr2] PEIRCE—RESPIRATION 97 
tity of heat represented by about 25 calories to warm its interior 
1° C. Thus, if the temperature in one of these calorimeters goes 
up 10° C., about 250 calories had been taken by the apparatus itself. 
This is known as the “heat equivalent” of the apparatus, and is a 
quantity which must always be added or subtracted in determining 
the amounts of heat liberated or taken up by a given organism, 
process, or reaction. 
In addition to the heat lost by radiation, etc., from the insulat- 
ing calorimeter, and the heat absorbed by the whole apparatus 
(flask, thermometer, and plug) and the air contained by it, the 
material within the flask will also absorb heat. It is necessary, 
therefore, to determine the heat equivalents of the material worked 
with, whether these materials are seeds or solutions. The solutions 
may contain nutritious substances in which such organisms as 
bacteria, yeasts, or fungi are living. In any case, the heat equiva- 
lents of all the substances or materials involved in the experiment 
must be ascertained. Thus, on one day I weighed out six lots of 
air-dry peas of 75 gr. each, putting these in crystallizing dishes, 
which I covered with glass lids and kept for 24 hours at a tempera- 
ture of about 18° C. Six Dewar flasks with thermometers and 
plugs, and containing some distilled water, were also placed under 
the same condition. After 24 hours I drained (but did not dry) 
the flasks, and put one lot of peas in each, reading the temperature 
of each. I assumed that the peas had in this time taken on a uni- 
form temperature before being put into the flasks. The slight 
differences in temperature, therefore, were presumably due to 
slight differences in the temperatures of the flasks and to slight 
differences in the amounts of heat due to friction in pouring the 
air-dry peas into the flasks. Then I poured 100 cc. of warm dis- 
tilled water at a known temperature into each flask and, when the 
temperature had become stable, recorded it. The data are as 
ollow: 
Flask Therm. Temp. Too cc. aq. Becomes Loss 
PRET pana I 19.7" 57.0" s-5 1170 cals, 
a eee 2 19.2 55-5 43-5 1200 
6 ee 3 19.3 56.0 44.2 r180 
Aoi eck co os 4 19.5 54.0 43.0 od gta 
Diet e et eeess 5 19.8 52.0 41.2 1080 
Oye eye. 6 19.8 49-5 40.4 gto 
