300 Dr. II. Herwig's Investigations on the Conformity 



PV 



Now wc have the relation —c \/a + t true (at least within 



the limitof errors of observation) for the vapours of the very differ- 

 ent bodies treated above, viz. alcohol, chloroform, and bisulphide of 

 carbon, the same value in all cases being assigned to the constant, 

 viz. c = '0o9o. Simultaneously with this there must hold the 

 other necessary relation, viz. p x v v -=c^ s/a-\-t, where c { means a 

 constant depending only on the density of each vapour, namely 



PV 



c, = ~„„- , r-. At the same time it follows that the pressure 



1 -0o9o (a + t) 



of perfectly saturated vapour is proportional to the square root 

 of the absolute temperature. From the relation p x v x = c s/a + t, 

 a more perfect understanding is afforded concerning the condi- 

 tion of perfect saturation, i. e. concerning one limiting condition 

 of these superheated vapours, so soon as the curve of maximum 

 tension is known. That important curve in the mechanical 

 theory of heat may then be constructed which exhibits the mu- 

 tual connexion of the magnitudes denoted above by p x and v v 

 provided we know the relation existing between jo, and t, i. e. 

 when the curve of tension is given. 



The values of i\ given in Tables I. a, II. a, III. a are taken 

 from the mass of vapour used on each occasion. Dividing these 

 values by the weight of the vapour in question, we shall obtain 

 the specific volumes, so called in the mechanical theory of heat, 

 of perfectly saturated vapour. With a kilogramme as the unit of 

 weight, we find the following specific volumes expressed in cubic 

 centimetres : 



Table IV. 



Alcohol. 



Temperature ... 



23° 



30° -5 



3 6 o. 4 | 41 o. 9 



47°-8 



57°-8 



62° -9 



69°-9 



Specific volumes. 



79879 



5-2379 



37984 



2-8589 21250 



1-3428 1-07(56 



0-802i 



Chloroform. 



Temperature 



30°-4 



39°-8 



49°-8 



64°8 

 0-1828 



Specific volumes .. 



0(5202 



0-4310 



03016 



Bisulphide of Carbon. 



Temperature 



8°-5 



14°2 



20°-l 



32° 



35°-9 



Specific volumes .. 



1-2343 0-9749 



0-7852 



5105 



0-4483 



