438 Heat of Vaporization of Liquid Hydrochloric Acid, 



-=£ was calculated from the following interpolation formula 



found by the method of least squares : — 



p= 28*451 + 0-4914 f + 0012463 fi, 



in the evaluation of whose constants the numbers in the 

 eleventh row in the above Table were omitted, because the 

 representative point in the p- and f-curve was much out of 

 the general course, p (calculated) in the following Table 

 are from the above interpolation formula, whose use is amply 

 justified by the numbers in the difference-column. 



The manner of variation of these numbers for r, as deduced 

 from the observations of Ansdell, is very remarkable. From 

 4° to about 14° the heat of vaporization increases, attains 

 there a maximum value, then decreases in a regular manner, 

 but from about 45° onwards it diminishes quite rapidly, as if 

 the gas were preparing for the critical point (51 0, 25), at 

 which the heat of vaporization is to vanish. 



Among those substances whose heat of vaporization was 

 investigated by MM. Cailletet and Mathias * we have no in- 

 stance like hydrochloric acid. It is much to be desired that 

 any one who has proper instruments in his possession will 

 take the trouble to decide whether the anomaly is real or 

 whether there were some mistakes in our data. 



* Journ. de Pkysiqv^ torn. v. 2 e serie, 1886. 

 2 e serie. 1890. 



Also, ibid. torn, ix, 



