263 
1909-10.] On an Electrically Controlled Thermostat. 
The figures refer to square centimetres of tinfoil, and are only relative. 
IV. The shunt in ohms, across the terminals of the secondary coil. A 
rise in the shunt means an increase in the current through the cell. This 
column along with Column YI. shows the elimination of heating effect. 
Y. The resistance with which the resistance of the cell was compared. 
The resistances used have the certificate of the Reichsamt in Berlin. 
YI. The actual readings of the bridge. The middle part of the bridge 
wire was used throughout, so that 1 in the fourth place of decimals corre- 
sponds to 1 in 25,000 of the resistance to be measured. 
YII. The concentration of the solution used in each case. The con- 
centration of the stock solution was determined gravimetrically with every 
precaution. The percentages of H 2 S0 4 found were : — 
(1) 60-78,; (2) 60-78 3 . 
Those that follow in the column were calculated from the weight of 
water added to the stock solution. As a check, the concentration of the last 
and most dilute solution was determined by precipitation with barium 
chloride as well as by dilution. The percentages of H 2 S0 4 found were : — 
(1) by dilution, 26*44 ; (2) gravimetrically 26-44. 
-i -i 
YIII. The specific conductivity in ohm cm multiplied by 10 4 . These 
were calculated from the means of the corresponding bridge readings. 
Table II. 
I. 
II. 
III. 
IY. 
Y. 
YI. 
Date. 
Hour. 
Capacity in 
parallel with 
Shunt on 
Secondary 
of Coil. 
Resistance. 
Reading of 
Bridge. 
(A) 
Cell. 
.(B) 
Resistances. 
1/3/07 
4.30 p.m. 
0 
15 
30 
1700 
4*8635 
33 
4.40 p.m. 
0 
15 
20 
1700 
4-8635 
2/3/07 
11.45 a.m. 
0 
16*5 
20 
1700 
4-8636 
55 
11.50 a.m. 
0 
16*5 
30 
1700 
4-8636 
5/3/07 
12.0 p.m. 
0 
5-5 
50 
1700 
4-8635 
33 
12.15 p.m. 
0 
5-5 
30 
1700 
4-8636 
18/3/07 
3.15 p.m. 
0 
7 
20 
1700 
4-8637 
3 ) 
1 
3.20 p.m. 
0 
7 
50 
1700 
4-8638 
In this table are given the determinations of the capacity of the cell. 
What has been said above for columns I. to YI. of Table I. applies also to 
vol. xxx. 18 
