Intelligence and Miscellaneous Articles. 165 



pressures (only about a centimetre higher than the maximum ten- 

 sion of these liquids), but we were unable to recognize any change in 

 the value of the coefficients of compressibility. — Comptes Rendus, 

 June 28, 1869. 



MEASUREMENT OF THE ELECTRICAL CONDUCTIVITY OF LIQUIDS 

 HITHERTO SUPPOSED TO BE INSULATORS. BY M. SAID-EFFENDI. 



M. Jamin has desired me to execute a method which he devised 

 for electrolyzing liquids of small conducting-power. The experi- 

 ments were made in the laboratory of the Sorbonne under his direc- 

 tion. The method is as follows : — 



The quantity of electricity which passes through a conductor is 

 proportional to its conductivity and its section, but is inversely as its 

 length. If the length be diminished and the section increased, a 

 current may be passed even through substances supposed to be insu- 

 lators. In the case of liquids this is effected by superposing two 

 large plates of platinum, kept apart by flannel or silk or glass, and 

 coiling them round a tube ; then, after being connected with the poles 

 of a battery, they are immersed in a voltameter. They thus repre- 

 sent a conductor, the length / of which is the thickness of the ma- 

 terial which separates the plates, and the section is twice their surface 

 2 5. In the present experiments / was about a millimetre, and 2 5 

 amounted to 195,000 square millimetres. When the roll was im- 

 mersed in a liquid the conductibility of which was c, the resistance 



w r as equal to , or to — . It was as if the conductivity 



^ 2s c 195000 c J 



had become about two hundred thousand times as great. 



By this means even the worst-conducting liquids are readily tra- 

 versed by the current. The following are the principal facts which 

 have been observed : — 



(1) Distilled water disengages with four Bunsen's elements as 

 much gas as acidulated water in an ordinary voltameter. It is there- 

 fore an electrolyte. But it becomes heated ; for a portion of the gases 

 recombines on the surface of the platinum. The volume of gas is 

 thus less with this pure water than with a voltameter containing 

 acidulated water placed in the circuit. As the intensity diminishes 

 the difference increases, and when the current is very weak there is 

 no apparent decomposition in the apparatus. 



(2) It is only when subjected to the action of powerful batteries 

 that alcohol has hitherto afforded signs of decomposition, which might 

 be attributed to the presence of foreign substances. With our appa- 

 ratus four elements disengage considerable quantities of hydrogen, 

 mixed with a small quantity of oxygen. 



(3) Oil of turpentine conducts far worse ; eight Bunsen's ele- 

 ments are necessary to produce a distinct decomposition. 



(4) Rectified oil of petroleum is decomposed with great ease. 

 The gas collected is inflammable, and during its combustion it de- 

 posits carbon upon the sides of the belljar in which it is contained. 

 This deposit may be due to the presence of petroleum-vapour in the 

 liberated gas. 



Further researches will give us the composition of the products 

 disengaged during these experiments. I have been especially en- 

 gaged in measuring the conductivity of these various liquids. 



