6 Prof. Buff on the Relation between the 



If we give the general formula (4) 



it,i ,1 273 + T , li 273 + T 



l0gP=l0 ^ + l0 ^273^T + ^ l0g 273^7 

 the following form — 



logP = logp+ — -log^^y, (6) 



or 



1+a 273+T 

 P = plO « ° g 273+^ (7) 



or, finally, as the first approximation, 



1 + ct 0-43437- 

 P=plO * " 2 ? 3 +', (8) 



it assumes a great similarity to the empirical formula 



7-4475 x * 

 e = 4 mm -525 x 10234-69+*, 



on which Magnus* founded his calculations, as well as to the 



partly theoretical formulae of Roche f, von WredeJ, and Holz- 



* 



mann§, which collectively have the form e — a. u m+nt . 



An essential peculiarity of formula (8) is, however, the sepa- 

 rate introduction of the coefficient a, the variation of which with 



the temperature was unknown to the former authors. 



i+« log 273+T 



The formula P=jolO a 2?3+t may be arranged more conve- 

 niently for use if we unite the numerator and the denominator 



of the expression^- in one coefficient a. We then have 



i t> 1 ,i 273 + T 

 log P = log;? + a log 273 + t ; 



or, if the tension is to be determined in terms of atmospheric 

 pressure, p = 760 millims. and 



i p 1 1 273 + T 



log- = logn=«log-^- (9) 



The following Table gives the values of a between —30° and 

 + 230° C. by increments of 5°, supposing p = 760, and £=100, 

 and T to be counted from 0° : — 



* Poggendorff's Annalen, vol. lxi. p. 225. [Translated in Taylor's 

 Scientific Memoirs, part xiv. p. 218.] 



f Ann. de Chim. et de Phys. Jan. 1830. 



X Poggendorff's Annalen, vol. liii. p. 225. 



§ Poggendorff's Annalen, Supplementary Volume ii. p. 183. [Taylor's 

 Scientific Memoirs, part xiv. p. 189.] 



