390 VAPOK-DENSITIES. 



at 219, 231, 240, respectively. Here the table in the Gomptes 

 Rendiis agrees substantially with that of the Lepons, but the experi- 

 ments of Horstmann show a divergence in the opposite direction. 

 In fact, the three columns of observed densities nowhere agree in 

 the direction of their divergence from the formula. 



The somewhat decided differences between the results of Horst- 

 mann and those of Cahours may be due in part to the different 

 methods of observation, especially to the entirely different manner 

 of applying the heat and measuring the temperature. But the higher 

 values obtained by Horstmann cannot be accounted for by too short 

 an exposure to the source of heat, for his experiments were made 

 with decreasing temperatures. 



The determinations of Bineau are taken from the same sources as 

 those on formic acid, the earlier determinations being distinguished 

 as before by parentheses. One of these (at 132) was made by the 

 method of Dumas, the other by that of Gay-Lussac. The smallness 

 of the observed densities appears due to the presence of water. (An 

 acidimetric test gave 295 parts of acid in 306.) The other experi- 

 ments were made with the same apparatus which was used with 

 formic acid and show even greater regularity in their results than 

 the experiments with that substance. Only in one case is the 

 influence of proximity to saturation seen, viz., at 20*5 and 10'03 mm , 

 the pressure of saturated vapor at this temperature being about 

 12'7 mm .* In the remaining fifteen observations of this series, not- 

 withstanding the very low pressures employed (from 2'44 to 11 "32), 

 the greatest difference between the observations and the formula 

 is "04, and the average difference *02. 



The two observations by Troostt were made by the method of 

 Dumas, but at pressures very low for this method. The results 

 obtained differ considerably from the formula, but not so much as 

 in the case of his experiments at low pressure with peroxide of 

 nitrogen. 



Table V contains the experiments of NaumannJ on acetic acid. 

 These consist of ten series (distinguished by the letters A, B, C, etc.) 

 of observations by Hoffmann's method. The temperatures of the 

 observations in the different series are for the most part the same, 

 so that for each temperature we have observations through a wide 

 range of pressures. Within each compartment of the table are given 



* This number is obtained from data given by Bineau by the same kind of interpola- 

 tion which was used for formic acid. 



t Comptes Rendua, vol. Ixxxvi (1878), p. 1395. 



% Lieb. Ann., vol. civ, p. 325. 



This is a modification of the method of Gay-Lussac, in which the heat is supplied 

 by a vapor bath. 



