2 8 PROPERTIES OF STEAM AND OTHER VAPORS. 



parts of Tables I and II where the heat of vaporization is stated to five 

 significant figures, while the data may appear to warrant only four; but 

 tin re- are conveniences in keeping one decimal place throughout these 

 tables for this property. 



Table II is made by interpolation from Table I, but the work has 

 been carried on in such a manner that it has practically the same degree 

 of accuracy. 



Table 1 1 1 was computed directly from the proper equation for each 

 degree Centigrade. English equivalents are added so that ready con- 

 versions can be made from one system to the other or a combination of 

 the two systems may be used. 



Tables IV to IX were taken from " Zeuner's Mechanische Warme- 

 theorie," making a correction for the true value of the mechanical equiv- 

 alent of heat, instead of Joule's earlier value, and adding columns of 

 entropy of the liquid. 



Tables X and XI for sulphur dioxide and ammonia were calculated by 

 the approximate method described earlier; though open to a considerable 

 degree of error they may be used till better information can be obtained. 



Tables XII and XIII do not appear to call for comment. 



Table XIV has been computed to aid in reducing data from tests where 

 pressures are recorded in inches of mercury. Pressures measured in 

 inches of mercury are usually less than that of the atmosphere and 

 the reading gives the vacuum, which is to be subtracted from the 

 barometric reading to find the absolute pressure in inches of mercury. 

 The table then gives the pressure in pounds per square inch which can 

 be taken to Table II to find the properties of steam. 



Table XV has been computed to reduce the labor of calculating the 

 volume of superheated steam. It gives the value of the factor 



,50.300.000 _ o -o833t 



in Knoblauch's equation on page 21 for English units. By aid of this 

 table the volume for a given temperature and pressure can be readily 

 computed. The inverse calculation assuming the volume cannot be 

 made directly, but such problems can be resolved by trial without much 

 labor. If the pressure and volume are assumed the temperature can 

 be found neglecting the correction term, and this will enable us to enter 

 the table at nearly the right place. 



