PROGRESS IN PHYSICAL CHEMISTRY. 225 



Critical state. — Another question having an important 

 bearing on the theory of gases and liquids has been the 

 subject of an animated controversy (7) during the past year. 

 It relates to the validity of the method of determining- the 



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critical temperature and to the condition of the substance at 

 the critical point. Batelli, Zambiasi and De Heen have 

 asserted that the critical temperature as determined in the 

 usual way depends on the amount of substance present in 

 the experimental tube, although their results regarding the 

 nature of the dependence do not agree among themselves. 

 Galitzine found no evidence of this effect, but concluded 

 that the meniscus disappears and reappears at different 

 temperatures. He further makes the remarkable statement, 

 based upon his work on ether, that at the same pressure 

 and temperature a substance may have different densities, 

 even if the temperature be above the critical temperature. 

 He therefore supports the view which has been, and is still 

 being, advocated by De Heen (8) that both liquid and gas 

 may exist above the critical temperature. Wesendonck (9) 

 has also described some anomalous appearances near the 

 critical point. 



In reply to statements such as these Ramsay and Young 

 (7) recall the fact that their own work, dealing with more 

 than twenty different liquids, gave no indication of the 

 above anomalies. These, they point out, might easily arise 

 if the experimental substance were not quite pure, especially 

 if it contained air or permanent gas, or if the whole of the 

 substance were not uniformly heated. Ramsay (10) has 

 further described an ingenious experiment with ether near 

 its critical point, which clearly demonstrates to what a large 

 extent the appearances within the experimental tube are 

 modified by slight inequalities in the temperature of the 

 substance. Villard (11) has also shown that with specially 

 purified carbon dioxide and nitrous oxide there are no 

 anomalies, and there is no difficulty in determining the 

 critical point, and Kuenen's observations (12) indicate that 

 the presence of permanent gas is the probable source of 

 most of the trouble to which reference has been made. It 

 may also be noted that the critical temperature of carbon 



