of Electrical Decomposition. 207 



of hydrogen. The experiment was repeated with acid of spec, 

 grav. 1*5; from the positive point 3-3 volumes were collected, 

 from the negative 2-6 ; the gas from the negative pole contracted 

 to 0*9 of its volume ; the residuum was pure oxygen ; that from 

 the positive contracted to 0*4 of its volume, the residue being 

 hydrogen.* 



8th. I now tried a saturated solution of sulphate of copper 

 with a few drops of sulphuric acid added ; a remarkable differ- 

 ence was shown in the conducting power of this solution as 

 compared with the dilute acid ; the contact breaker of the pri- 

 mary coil gave very minute sparks, unattended with the usual 

 snapping noise ; it was much as if the terminals of the secondary 

 coil had been united by a metallic connexion ; and the supe- 

 riority of the conducting power of the solution of sulphate of 

 copper in this experiment over dilute sulphuric acid was far 

 greater than is shown in ordinary electrolysis by the voltaic 

 battery. The coated point was positive, the plate negative ; the 

 gas from the positive point detonated, leaving a very slight 

 residue; but on the interior of the collecting tube, near the 

 point, was a deposit of pulverulent metallic copper. On the 

 negative plate there was no deposit, and no gas was given off 

 from it. Here the copper deposit was evidently a reduction oc- 

 casioned by the excess of hydrogen, but there was no symptom 

 of any effect produced by any equivalent to it of oxygen. 



9th. With a solution of caustic potash the coated point, which 

 was positive, gave a gas which contracted to 0*32 of its volume, 

 the residue being hydrogen ; the plate, which was negative, gave 

 off a mere trace of gas. 



10th. Two plates were used as the terminals of the secondary 

 coil in dilute sulphuric acid, instead of a plate and a point. No 

 gas was given off from either, though the experiment was con- 

 tinued for several hours. 



11th. I could detect no difference in the solutions employed 

 before and after the experiment ; but as the sulphuric acid might 

 be expected to mask the effect of any oxygenated compound 

 which might result from the absorption of oxygen, which took 

 place in all these experiments except those where the strong 

 solutions of sulphuric acid were employed, and as pure distilled 

 water would give no effect, I tried the effect of the spark passed 

 through aqueous vapour. Some distilled water was boiled and 

 placed under the receiver of an air-pump, with a coated point 

 and plate of platinum enclosed in a tube filled with the liquid, 

 and inverted ; the point and plate communicating respectively 

 with the upper and under plate of the receiver, and thence 

 brought into metallic communication with the ends of the 

 secondary coil. 



