134 
MESSRS. J. HOPKINSON AND E. WILSON ON THE 
Table IX.—Castor Oil. 16th November, 1896. 
^ microfarad Condenser; Kg = large slide Condenser. 
K = '000287 microfarad from Hig’h Frequency Resonance Experiment. 
Time of contact, i Temperature of Castor Oil, 6° C. 
Turns 
of 
milled 
head. 
Time in 
seconds. 
Large 
slide 
position 
K^. 
a 
in 10® 
ohms. 
/ 
Resistance of 
Flask e in 10® ohms. 
1 
c 
in 10“® 
(rD). 
If* 
J c 
1 F = 
~ ■ K ^ \Ldt 
^ ^ \ 
From 
a + Ac 
a + c 
From 
Ki 
a — t . 
^2 
Area in 
square 
centims. 
-Ae ' 
m.f. . 
m m.f. 
0 
•00002 
430 
•015 
1/100 
- 2-7 
3-34 
•3* 
1 
O 
•00035 
160 
•095 
1/361000 
431 
43-1 
•023 
6-2 
•000025 -00031 
1 
•00099 
40 
•110 
92'7 
•0108 
8-5 
-000034 -00032 
D 
•0028 
40 
•223 
188 
•0053 
12 
•000048 -00033 , 
o 
O 
•006 
40 
•320 
270 
•0037 
14 
•000056 -00034 
5 
•01 
40 
•460 
388 
•00258 
7 
40 
•620 
523 
•0019 
slightly 
greater 
than 
y 
40 
•620 
Glycerine. 
This glycerine was obtained from Messrs. Hopkin and Williams, and has been 
tested for purity and dried very carefully by M.r. Herbert Jackson, of the Chemical 
Department of King’s College, London. The platinum plates, after careful cleaning 
in benzene, caustic-potash, and water were thoroughly dried and submerged in the 
glycerine in a beaker, the whole being placed in a glass receiver over a strong 
dehydrating agent. After exhaustion, just sufficient air was admitted to render the 
space inside sufficiently non-conducting to stop discharge between the terminals of 
the condenser which are sealed into glass tubes supported by an indiarubber stopper. 
The short-contact experiments show that the apparent resistance is 60,000 ohms, 
whether the time of contact be '00002 or *001 second, showing that there is no 
residual charge. The resonance experiments with high frequency give '005 micro¬ 
farad fur the capacity with glycerine, whereas with air the condenser had '000082 
capacity ; the specific inductive capacity is, therefore, about 60. A test made as with 
castor oil with a Kulimkorff at low frecjuency was difficult, but a fair approximation 
* Taken from , since the negative value obtained from - is untrustworthy, probably 
Kg U + 0 
owing to K being' still too large. To satisfy Maxwell's law, K should = '000176 microfarad. 
