﻿Liquid Films between Iridio-platinum Electrodes. 321 



These distances are entered in the tables following in units 

 which are O'Ol p (fz = micron = joVo mm )• 



The surfaces of p, q presented to one another are renewed, 

 as shown above, by rotations and another discharge is made. 



Most of the liquids used are of commercial quality, and 

 are purified as shown above ; others were obtained specially 

 pure. The following liquids were tested : — 



Vegetable Oils. — Olive oil, castor oil, linseed oil, rape oil. 

 Also turpentine, fusel oil, and oil of resin. 



Animal Oils. — Cod-liver oil, neats-foot oil. 



Mineral Oils. — Paraffin, transformer oil. 



A Homologous Series. — Pentane (C 5 H 12 ) ; hexane (C 6 H 14 ) ; 

 heptane i(J 7 H 16 ); octane (( "gHis)* These were obtained from 

 C. A. F. Kahlbaum, Berlin. Hexane and octane were 

 specially pure, being derived from propyl iodide and octyl 

 iodide respectively ; while heptane and pentane were obtained 

 from petroleum. 



Varnishes. — Of these armaeell and ohmaline are obtained 

 from Griffiths Bros., Bermondsey, London ; while Sterling- 

 varnish is made by The Sterling Varnish Co., Manchester. 

 Though these are made to insulate when dry, they all have 

 great dielectric strength when liquid, as shown in the 

 curves (fig. 5). 



Table I. 

 1= spark-length stated in units of 0'01/z. 



P.D. 



in volts. 



I. 



















Olive 



Linseed 



Castor 



Erpe 



Turpen- 



Fusel 



Air. 





Oil. 



Oil. 



Oil. 



Oil. 



tine. 



Oil. 



375 



560 



550 



570 







550 



1300 



350 



510 



475 



520 



610 



520 





1100 



300 



445 



350 



400 



430 



420 



;;';'{ 



160 . 250 

 480 . 320 



275 















120 



2-">0 



400 



3C0 



350 



400 



340 



300 



118 



200 



... 



220 





300 



220 



255 



100 



186 



340 





318 





165 







150 



290 



190 



275 



220 



120 



205 



80 



125 



235 



150 



210 





100 





48 



100 



200 



95 



170 



lib 



90 



150 



46 



75 



145 





150 



115 



80 



110 



36 



70 



140 















68 



115 















66 



93 















62 



80 





110 











50 



60 



56 



58 



45 



55 



80 



14 



25 



27 



27 



35 





27 



35 



8 



10 



11 















Phil. Mag. S. 6. Vol. 12. No. 70. Oct. 1906. 



