III. On vacua as indicated by the mercurial siphon-gauge and the electrical discharge

• Published in: Proceedings of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1860
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1098/rspl.1859.0053; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1859.0053

That the varied condition of the stratified electrical discharge is due to the relative but always imperfect condition of the vacuum through which it is passed, is exemplified by the changes which take place in the form of the striæ while the potash is heated in a carbonic acid vacuum-tube. In order, if possible, to measure the pressure of the vapour, I had a carefully prepared siphon mercurial gauge sealed into a tube fifteen inches long, at an equal distance between the two wires A, B. This tube was charged with carbonic acid in the manner described by me in a former communication. When exhausted by the air-pump and sealed, it showed a pressure indicated by about 0·5 inch difference in the level of the mercury; the potash was then heated; the mercury gradually fell, until it became perfectly level.