Chemistry mid Physics. 383 



bon, then an increase in the length of the carbon layer or a 

 decrease in the velocity of the gas-current, should increase the 

 amount of monoxide produced, as is shown in the 7th and 9th 

 experiments. 3d, that the reduction increases with the tempera- 

 ture. The paper concludes with a discussion of the thermochem- 

 ical questions involved in the results obtained. — JBer. Berl. Chem. 

 Ges., xviii, 1647, July, 1885. g. f. b. 



4. The Decomposition of Carbon dioxide by the Electric 

 spark. — In consequence of an observation showing that no ex- 

 plosion is propagated by a spark in a mixture of carbon mon- 

 oxide and oxygen which has been dried over phosphoric oxide, 

 made by Dixon, he has undertaken, assisted by Lowe, the study 

 of the action of the electric spark upon carbon dioxide when 

 similarly dried. The gas carefully dried over phosphoric oxide, 

 was placed in a eudiometer and, by means of a chain composed 

 of short pieces of platinum fused into small glass beads, was sub- 

 mitted to the action of a series of induction sparks. The amount 

 of decomposition varied from time to time, but approached no 

 fixed limit; the maximum decomposition being about 45 per cent 

 under 100 mm. pressure. Placing a condenser in the secondary 

 circuit, diminished the effect. To test the effect of varying the 

 length of the spark, a eudiometer was next employed which had 

 two pairs of platinum wires, the ends being 1*5 mm. and 6 mm. 

 apart respectively. On passing the spark through 52*10 c. c. of 

 the perfectly dried gas, between the former terminals, the vol- 

 ume began soon to increase, attaining finally 62*34 c. c. ; showing 

 a decomposition of 39 08 per cent of the C0 2 into CO and O. In 

 a second experiment in which the sparks passed continuously for six 

 hours, the decomposition was 33 97 per cent. When the spark 

 passed through the wider space for five hours, the decomposition 

 was 30*20 per cent. Returning to the shorter spark the coil was 

 left running over night with one cell of battery. In the morning 

 it had stopped and the decomposition was 43*33 per cent. In 

 these experiments the pressure was about 500 mm. and the tem- 

 perature varied from 10° to 15°. It is therefore clear that the 

 shorter spark produced the greater decomposition. Since the 

 variations of volume due to changes in the nature of the electric 

 discharge, mask the effect of varying pressures, a differential 

 process was resorted to. Two similar eudiometers were prepared 

 and fitted with wires made of platinum-iridium alloy, each termi- 

 nating in a 2 mm. ball, the distance between them being the same 

 in the- two tubes. When a series of sparks was sent simultane- 

 ously through both tubes containing dry C0 2 , the effect was the 

 same in both, the volumes varying together so long as the pres- 

 sure was preserved constant. The greater decomposition was 

 produced by the feebler spark and under the less pressure. When 

 100 volumes of dry C0 2 were placed in one tube and 150 volumes 

 of a dry mixture of carbon monoxide and oxygen were placed in 

 the other, and a series of sparks from the same coil was passed 

 through both, the volume of C0 2 increased and that of the CO 



