364 



R. Clausius on the Application of the 



Art. XXVIII.- — On the Application of the Mechanical Theory of 

 Heat to the Steam .Engine ; by P. Clausius. 



[Continued from p. 203.J 



27. The influence which the difference of the pressure in the 

 boiler and in the cylinder exerts upon the work, has been treated 

 probably most completely up to this time in the work of de Pam- 

 bour (Theorie des Machines a vapeur), and I may be permitted 

 before I myself take up the subject, to state in advance the most 

 important points of this mode of treating it, only with a some- 

 what different notation and with the omission of the magnitudes 

 which relate to the friction, in order to be able the more easily 

 to show how far the theory no longer corresponds to our more 

 recent knowledge of heat, and at the same time to connect with 

 it the new mode of treating the subject, which in my opinion 

 must take its place. 



28. The two laws mentioned already at the beginning of this 

 paper, which at that time were pretty generally applied to steam 

 form the foundation of de Pambour's theory. First, the law of 

 Watt, that the sum of the free and latent heat is constant. From 

 this law, the conclusion was drawn, that if a quantity of steam 

 at the maximum density be enclosed in a shell impenetrable to 

 heat, and the cubic contents of this shall be increased or dimin- 

 ished, the steam will in this case be neither over-heated nor 

 partially precipitated, but will remain exactly at the maximum 

 density, and that this would take place quite independently of 

 the mode in which the change of volume may occur, whether the 

 steam had to overcome thereby a pressure corresponding to its 

 expansive force or not. Pambour supposed that the steam be- 

 haved in the same way in the cylinder of the steam engine, inas- 

 much as he did not assume that the particles of water which in 

 this case are mixed with the steam could exert a perceptible 

 changing influence. 



In order now to be able more nearly to express the connection 

 which exists for steam at the maximum density, between volume 

 and temperature or volume and pressure, Pambour applied in 

 the second place the laws of Mariotte and Gray Lussac to steam. 

 From these we obtain the equation 



/™x n n 10333 273 -f- if 



(28.) , = 1 ,696.^-.^_, 



if we assume with Gray Lussac the volume of a kilogram of steam 

 at 100°, at the maximum density, to be 1,696, and consider that 

 the pressure thereby exerted by one atmosphere upon a square 

 meter is 10,33-3 kilograms, and if we denote for any other tem- 

 perature t t the volume and the pressure, assuming the same units, 



