468 On the Thermodynamics of Volatile Liquids. 



fig. 1, which has been employed industrially in the production 

 of ice by means of sulphurous acid. The observations were 

 made with extreme accuracy during the space of one month 

 at La Ciotat, near Toulon, by the care of M. Vesigne^ Manager 

 of the dockyards of the Messageries Maritimes. 



One engine produced 36 kilogrammes of ice per hour, under 

 the following conditions : — 



Temperature of the refrigerant — 10° ; temperature of the 

 condenser + 35°. 



Pressure at — 10° = 762*49 millims. ; pressure at 35° = 

 4014-78 millims. 



Specific heat c = 035 ; \ at — 10° for sulphurous acid 

 = 102; and 5 = 2-112. 



The equation of the quantity of heat absorbed in one minute 

 to produce 36 kilos of ice per hour is given by 



P 102 - p 45 x 0-35 = 60 calories, 



in which p is the weight of sulphurous acid volatilized. We 

 find p = 694 grammes. Substituting this value of p in the 

 equation of the work T for 1 second, we have 



1AQQQ 7 /4014-78\ 

 10333 ^H76W)_ 



T = — -J- = 69*44 kilogrammetres. 



1-293x2-112x60 6 



We will remark that ice proceeding from the solidification 

 of water at 21° absorbs 100 calories per kilogramme; con- 

 sequently the engine absorbs 1 calory per second; and by 

 Carnot's cycle we have the following relation, 



T 1 (*'-*) E_45x 433-5 M15ri ., 



= 274 4- £ — 309 = kilogrammetres. 



By the cycle of sulphurous acid we find 69*44 k. ; the co- 

 incidence is almost absolute. Let us add that in practice the 

 ice-engine consumes under these conditions one horse-power 

 of steam, or about 75 kilogrammetres. 



From all that precedes we can draw the following con- 

 clusions : — 



1. Cohesion is a constant quantity for all liquids. 



2. The derivate of the Napierian logarithm of the quotient 

 of the tensions by the temperatures is constant for all liquids 

 at the same pressure and the same temperature. 



3. The latent heats of all liquids, brought to one and the 

 same pressure, multiplied by the atomic weight at the same 

 temperature, give a constant product. 



4. For all liquids, the difference of the internal latent heats 

 at any two temperatures, multiplied by the atomic weight, is a 

 constant number. 



