534 Critical Temperatures and Thermal Expansions. 



paper published in the Annales, or they would not have waited 

 two years before replying ; and we believe also that had they 

 read the paper in its entirety they would not have found it 

 necessary to send any reply. We had no intention of criticising 

 the work of Messrs. Thorpe and Riicker, but merely of 

 showing by numerous examples the limits within which the 

 formulas of Mendelejeff, and of Thorpe and Riicker, were 

 applicable. 



We believed that our inquiry would result in some utility, 

 because it was not clear whether the formula of Mendelejeff, 

 which was deduced from the comparison of the expansion of 

 liquids, measured under a pressure of one atmosphere, could 

 be applied to the expansion of liquids measured under a 

 constant, or uniform, pressure, although not of one atmo- 

 sphere. 



We proved that the formula of Mendelejeff is valueless for 

 showing the results of the experiments of Hirn, who has 

 carefully studied the expansion of certain liquids under a 

 constant pressure of 11 metres of mercury. 



This fact appeared, and still does appear, to us to detract 

 much from the general applicability of the formula of Men- 

 delejeff for representing the expansion of liquids, which there- 

 fore we cannot consider otherwise than as empirical, and 

 applicable only within narrow limits, but having with regard 

 to the formulas more commonly adopted the merit of greater 

 simplicity. 



We were well aware that the formula of Mendelejeff and 

 that of Messrs. Thorpe and Riicker (which is applicable within 

 the same limits as that of Mendelejeff) were not applicable to 

 water, and we especially called attention to the fact in the 

 note at page 98 of our article, and also at page 102. 



The formula of Messrs. Thorpe and Rucker for calculating 

 the critical temperature leads to results which agree exactly 

 with those obtained from experiments at temperatures lower 

 than the normal boiling-point. We have already applied 

 that formula for the calculation of critical temperatures of 

 all liquids of which the thermal expansion has been studied. 



We shall feel obliged by your kindly publishing the above 

 statement. Yours &c, 



A. Bartoli. 

 E, Stracciatt. 



