[ 426 ] 



LIV. On the Application of the Mechanical Theory of Heat to 

 the Steam-engine, By R. Clausius. 



[Concluded from p. 354.] 

 46. TIETHEN the tension series for the vapour of any liquid 

 ▼ ▼ is known with sufficient accuracy, the values of the 

 magnitudes ff and T^ for the several temperatures can be calcu- 

 lated from it, and arranged in tables in the same manner as is 

 usually done with the values of jo. 



In the case of steam, hitherto almost solely used for machines, 

 and for the interval of temperature extending from 40° to 200° C, 

 between which the application takes place, I have, with the help 

 of Regnault's tension series, made such a calculation. 



Strictly, I ought to have differentiated according to / the for- 

 mulae which Regnault used in calculating the several values ofp 

 below and above 100° C, and then to have calculated ff by means 

 of the new formulse thus obtained. But as it appeared to me 

 that those formulse did not fulfil their pui'pose perfectly enough 

 to justify so large an amount of labour, and as the calculation 

 and institution of another suitable formula would have been still 

 more tedious, I contented myself with using the numbers already 

 calculated for the pressure in order approximately to determine 

 the differential coefficient of the pressure. For example, p^^ 

 and jt?j48 being the pressures for the temperatures 146° and 148°, 

 I have assumed that the magnitude 



2 



represents with sufficient accuracy the value of the differential 

 coefficient for the mean temperature 147°. 



In doing this, I have for temperatures above 100° used the 

 numbers given by Regnault himself*. With respect to the values 

 below 100°, Moritzf has lately drawn attention to the fact that 

 the formula employed by Regnault between 0° and 100° was, 

 especially in the vicinity of 100°, somewhat incorrect in conse- 

 quence of his having used logarithms of seven places in calcula- 

 ting the constants. In consequence of this, Moritz has calcu- 

 lated those constants with logarithms of ten places, basing his 

 calculations on the same observed values ; and he has published 

 the values of ^ — as far as they differ from Regnault's, which only 

 occurs above 40°, — thus deduced from the corrected formulse. I 

 have used these values. 



As soon as g is calculated for the several temperatures, the 



* M^. de VAcad. des Sciences, vol. xiii. p. Q2b. 

 t Bulletin de la Classe Fhysico-matMrnatique de VAcad. de St. P^terS' 

 bourff, vol. xiii. p. 41. 



