Photochemical Researches.--Part IV. [Abstract] [abstract]

Robert W. Bunsen, Henry Enfield Roscoe
1859 Proceedings of the Royal Society of London  
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more » ... out Early Journal Content at http://about.jstor.org/participate--jstor/individuals/early-journal--content. JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not--for--profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. heat of considerable intensity was permitted to send its rays through the tube to the pile at its opposite extremity; the deflection of the needle was very energetic. The second pile was now caused to approach the source of heat until its current exactly neutralized that of the other pile, and the needle descended to zero. Here then we had two powerful forces in perfect equilibrium; and inasmuch as the quantity of heat in action was very considerable, the absorption of a small fraction of it might be expected to produce a sensible effect upon the galvanometer-needle in its present position. When the tube was exhausted, the balance between the equal forces was destroyed, and the current from the pile placed at the end of the tube predominated. Hence the removal of the air had permitted a greater amount of heat to pass. On readmitting the air, the needle again descended to zero, indicating that a portion of the radiant heat was intercepted. Very large effects were thus obtained. I have applied the same mode of experiment to several gases and vapours, and have, in all cases, obtained abundant proof of calorific absorption. Gases vary considerably in their absorptive power-probably as much as liquids and solids. Some of them allow the heat to pass through them with comparative facility, while other gases bear the same relatioln to the latter that alum does to other diathermanous bodies. Different gases are thus shown to intercept radiant heat in different degrees. I have made other experiments, which prove that the selfsame gas exercises a different action upon different qualities of radiant heat. The investigation of the subject referred to in this Note is now in progress, and I hope at some future day to lay a full description of it before the Royal Society. VIII. " Photochemical Researches."-Part IY. By ROBERT W. BUNSEN, For. Meimib. R.S., anrd HENRY ENFIELD ROSCOE, Ph.D., Professor of Chemistry ini Owens College, Manchester. Received May 26, 1859. (Abstract.) In the three communications * which they have already made to the Royal Society upon the subject of photochemistry, the autlhors showed * Phil. Trans. 1857, pp. 355, 381 and GOle
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