New iLleElric Experiments. 201 



water. The fixed air in tlm experiment was obtained by 

 heat from a mixture of charcoal-duft well dried and freed 

 from air, and red precipitate expofed to heat. In order that 

 the vefTels might be freed from all moifture they were ex- 

 pofed to a ftrong heat, and the quickfilver employed in the 

 apparatus was boiled. In order to try whether the car- 

 bonic acid obtained contained any water, ftrong fparks were 

 made to pafs through it ; and the operator watched with 

 great care to obferve whether water would be produced, and 

 whether a long fpiral iron wire, employed in. the apparatus, 

 would be oxydated. The fixed air itfelf occupied in the tube 

 the length of nearly 4 inches 6\ lines before being fubjedfced 

 to electricity, and the diameter of the tube was 7 lines. As 

 foon as the fparks entered it, the operators faw with afto- 

 nifhment that the column of air gradually increafed, and, 

 after being electrified 16 minutes, the air in the tube occu- 

 pied a fpace of 5 inches 1 line, which gave an increafe of al- 

 moft T ~ of the whole. They then wafhed the fixed air in 

 cauftic alkali till its volume ceafed to be leflened, and the 

 reliduum in the tube amounted to two inches. The flame 

 of a taper being then applied to the aperture, this electrified 

 refiduum inflamed, and therefore (bowed that it confifted en- 

 tirely of unmixed inflammable air. As this refult did not 

 coincide with what we are taught by theory, it was relblved 

 to repeat the experiments, and to employ double care in 

 order to drive off the moifture. But as greater attention 

 was now paid to what took place during the revival of the 

 mercury, it was obferved that fome vapour was, depofited in 

 the upper part of the flafk employed for the experiment, as 

 well as in the tube through which the produced air was 

 made to pafs. It was fuppofed on the firft view that this 

 vapour was fublimated mercury; but it foon formed itfelf into 

 fmall drops of water, which increafed in fize, fo that no doubt 

 now remained refpecting the production of water. The re- 

 daction was then fufpended, and the whole apparatus was 

 heated and dried as well as pofiible; but, on continuing the 

 experiment, the drops again appeared. Now, as it was im- 

 poflible that this water could arife from the moifture of the 

 veflels, it feems proved to Van Marum that carbon not only 

 Vol. VIII. D d contains 



