102 On the Liquefaction and Solidification [1844. 



The fluid carbonic acid was supplied to me by Mr. Addams, 

 in his perfect apparatus, in portions of about 220 cubic inches 

 each. The solid carbonic acid, when produced from it, was 

 preserved in a glass ; itself retained in the middle of three con- 

 centric glass jars, separated from each other by dry jackets of 

 woollen cloth. So effectual was this arrangement, that I have 

 frequently worked for a whole day of twelve and fourteen hours, 

 having solid carbonic acid in the reservoir, and enough for all 

 the baths I required during the whole time, produced by one 

 supply of 220 cubic inches*. 



By the apparatus, and in the manner now described, all the 

 gases before condensed were very easily reduced, and some 

 new results were obtained. When a gas was liquefied, it was 

 easy to close the stopcock, and then remove the condensing 

 tube with the fluid from the rest of the apparatus. But in 

 order to preserve the liquid from escaping as gas, a further 

 precaution was necessary ; namely, to cover over the exposed 

 end of the stopcock by a blank female screw-cap and leaden 

 washer, and also to tighten perfectly the screw of the stopcock 

 plug. With these precautions I have kept carbonic acid, 

 nitrous oxide, fluosilicon, &c. for several days. 



Even with gases which could be condensed by the carbonic 

 acid bath in air, this apparatus in the air-pump had, in one 

 respect, the advantage ; for when the condensing tube was lifted 

 out of the bath into the air, it immediately became covered with 

 hoar-frost, obscuring the view of that which was within ; but 

 in vacuo this was not the case, and the contents of the tube 

 could be very well examined by the eye. 



Olefiant Gas. This gas condensed into a clear, colourless, 

 transparent fluid, but did not become solid even in the carbonic 

 acid bath in vacuo ; whether this was because the temperature 

 was not low enough, or for other reasons referred to in the 

 account of euchlorine, is uncertain. 



* On one occasion the solid carbonic acid was exceedingly electric, but I 

 could not produce the effect again : it was probably connected with the pre- 

 sence of oil which was in the carbonic acid box ; neither it nor the filaments 

 of ice which formed on it in the air conducted, for when touched it preserved 

 its electric state. Believing as yet that the account I have given of the cause 

 of the electric state of an issuing jet of steam and water (Phil. Trans. 1843, 

 p. 17) is the true one, I conclude that this also was a case of the production 

 of electricity simply by friction, and unconnected with vaporization* 



