. The principles of chemistry . many such experi-ments in which open vessels containing pounds of liquid oxj-gen were employed, and infollowing the progress made in researches conducted at low temperatures, it is my firmimpression that the study of many phenomena at low temperatures should widen thehorizon of natural science as much as the investigation of phenomena made at thehighest temj)eratures attained in the Aoltaic arc. ^^ The investigations of S. Wroblewski in Cracow give reason to believe that Pictetcould not have obtained liquid hydrogen in the interior of his apparatus, and that if
. The principles of chemistry . many such experi-ments in which open vessels containing pounds of liquid oxj-gen were employed, and infollowing the progress made in researches conducted at low temperatures, it is my firmimpression that the study of many phenomena at low temperatures should widen thehorizon of natural science as much as the investigation of phenomena made at thehighest temj)eratures attained in the Aoltaic arc. ^^ The investigations of S. Wroblewski in Cracow give reason to believe that Pictetcould not have obtained liquid hydrogen in the interior of his apparatus, and that if hedid obtain it, it could only have been at the moment of its outrush due to the fall intemperature following its sudden expansion. Pictet calculated that he obtained a tem-perature of —140°, but in reality it liardljfell below —120°, judging from the latestdata for the vaporisation of carbonic anhydride under low pressure. The differencelies in the method of a^fermining low temperatures. Judging from other properties of. Fi(i. 25.—Cuilletets apparatusfor liquefying gases. 140 PRINCIPLES OF CHEMISTRY these means the gases of the atmosphere may be kept in a liquid statefor a long time. This is due to the fact that the absolute boiling pointof hydrogen lies lower than that of all other known gases, which alsodepends on the extreme lightness of ^* hydrogen {see Note 34), one would think that its absolute boiling point lies far below—120°, and even —140° (according to the calculation of Sarrau, on the basis of its com-pressibility, at —174°). But even at —200° (if the methods of determining such lowtemperatures be correct) hydrogen does not give a liquid even under a pressure of severalhundred atmospheres. However, on expansion a fog is formed and a liquid state attained,but the liquid does not sej^arate. ^^ After the idea of the absolute temperature of ebullition {tc, Note 29) had beenworked out (about 1870), and its connection with the deviations fro
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