HEAT OF WATER, WITH EXPERIMENTS BY A NEW METHOD. 
25 
For regulating the temperature of tlie cold current, an electric temperature 
regulator was employed of the same type as that used in the continuous-electric 
method, which had been specially designed to prevent hunting. With a 32 c.p. lamp, 
and suitable adjustment of the cooling water, currents up to 20 gr./sec. could be kept 
steady to a few thousandths of 1° C. for considerable periods, over a range from 
20° C. to 35° C. But this was not such an easy matter as might be imagined, owing 
to variations of temperature of the cooling water. 
During the months of May, June, and July, 1911, upwards of 150 complete sets of 
readings were taken, each for a single flow. The upper limit of temperature was 
always nearly 100° C., but the lower limit was varied from 25° C. to 35° C. The 
flow was varied from 1 c.c./sec. to 20 c.c./sec. It is a great advantage of the method 
that it permits the flow to be so widely varied without introducing any serious 
experimental difficulties, but the largest flows were somewhat difficult to regulate, 
and there was no material gain in accuracy beyond about 10 c.c./sec., at which point 
the limit of accuracy of the thermometric readings corresponded with the limit of 
reading the total heat curves. Many variations were tried in the disposition of the 
apparatus, with corresponding variations in the heat-loss, which, even without jackets 
or lagging, seldom exceeded 1 per cent, of the heat-exchange for the largest flow. 
The results of all these experiments were so nearly similar that it will suffice to give 
one example of the detailed readings. The following readings were taken with the 
jacket-tube J surrounding the exchanger, but without lagging or jackets on the 
thermometer-pockets;— 
Obseevations of July 3, 1911. 
Flow gr./sec. Q 
10-44 
10-47 
7-43 
4-08 
2-55 
1-240 
Thermometer ti . . 
-H 99-980 
99-972 
99-901 
99-702 
99-451 
98-762 
„ t-2 . . 
- 68-979 
68-989 
67-107 
64-383 
62-996 
61-763 
» h ■ • 
-f 25-442 
25-445 
25-466 
25-524 
25-548 
25-587 
»J ^^4 • • 
-56-452 
56-436 
58-205 
60-628 
61-567 
61-486 
Sum 2 /. 
- 0-009 
- 0-008 
+ 0-055 
+ 0-215 
+ 0-436 
+ 1-100 
'Zdh from curve . . 
+ 0-152 
+ 0-152 
-h 0-153 
+ 0-154 
+ 0-152 
+ 0-148 
Heat-loss X. . . . 
1-49 
1-50 
1-54 
1-51 
1-50 
1-55 
The above table includes observations for five different values of the flow. Each 
flow was maintained steady for about haff-an-hour, during which time two measure¬ 
ments of the flow were taken, and four sets of readings of the thermometers. The 
flows generally agreed to 1 in 500, and the thermometers seldom varied more than 
0°'01 C. in half-an-hour. In the above example the readings for the maximum flow 
were continued for over an hour. Such changes in the thermometer readings as 
occurred during each flow were due partly to change in the barometer and partly to 
change in the temperature of the cooling water, which also made it necessary to reset 
the regulator between each flow, as indicated by the readings of the thermometer 
VOL. CCXII.-a. 
E 
