[ 503 ] 



LI. Intelligence and Miscellaneous Articles. 

 ON THE THERMAL BEHAVIOUR OF LIQUIDS. 



To the Editors of the Philosojrfiical Magazine. 



Gentlemen, 

 TN answer to the letters of Drs. B. Galitzine and P. de Heen in 

 -*- the April number of this Journal, we beg to make thefollowiDg 

 remarks : — 



It is quite true, as stated by Dr. Galitzine, that our criticism 

 of- the arrangements employed to obtain constant high tempe- 

 ratures does not apply to him (provided that the naphthaline 

 employed by him as a jacketing a apour was pure). This, however, 

 we pointed out in our paper, at the same time calling attention to 

 the fact that the method was, with certain modifications, that 

 employed and recommended for many years by ourselves. We 

 think, however, that Dr. Galitzine's results are open to criticism 

 on the following grounds : — (1) The complete elimination of alcohol 

 from ether is not an easy matter, and cannot be effected by the 

 action of metallic sodium ; but no other method of purification is 

 mentioned in his paper. The last trace of alcohol may be removed 

 by shaking the ether twenty or thirty times with small quantities of 

 water, or by repeated distillation over phosphorus pentoxide ; but Ave 

 do not know of any other method. (2) Although we fully appre- 

 ciate the great pains taken by Dr. Galitzine to purify his ether from 

 air, yet we doubt whether any method involving the sealing of a 

 glass tube is capable of giving perfectly satisfactory results. In the 

 Trans. Chem. Soc. for 1891, p. 37, a new method of determining 

 the specific volumes of liquids and of their saturated vapours was 

 described by one of us ; and experience has shown that the chief 

 difficulty in this method is the necessity of sealing the tube con- 

 taining the liquid. The vapour of the liquid may undergo slight 

 decomposition ow T ing to the high temperature, or a trace of air 

 may be expelled from the glass. It has been frequently observed 

 in the experiments carried out by this method that when a minute 

 quantity of air or permanent gas is present, the attainment of the 

 final state of equilibrium is greatly retarded. It has also been 

 observed that the retardation increases with the amount of perma- 

 nent gas present, and that if there is a comparatively large amount 

 (though actually a very small one), the results are rendered entirely 

 untrustworthy. 



The influence of the permanent gas has also been found to 

 increase rapidly as the critical point is approached, though it may 

 be very marked at much lower temperatures. This question has 

 been shortly discussed by one of us (Trans. Chem. Soc. 1891, 

 p. 128), and very fully by Dr. J. P. Kuenen ( Verslagen der Afde.elwg 

 JSaturkunde der Kon. AJcademie, Leiden, April 1892, p. 422 ; June 

 1892, p. 15 ; Oct. 1893, p. 85) ; and we fully agree with Dr. Kuenen 

 in the great importance he attaches to retardation. 



