Knowledge of the Specific Volumes of Steam. 



for of the twenty-two only seven agree with his, six are not 

 comparable, four disagree slightly, and five disagree completely. 

 We have thus left only the experiments of Battelli and 

 those of Ramsay and Young. Some at least of the determina- 

 tions of the former at low pressures are incorrect, for they give 



values of 7^ which differ too much from a perfect gas. In 



the case of Ramsay and Young we are confronted by a diffi- 

 culty at the very start. I take the following quotation from 

 them (reference, p. 122) : 



" The weight of the water in the tube was ascertained by 

 determining the products of pressure and volume, altering the 

 volumes ; and this was repeated at different temperatures. 

 Assuming that if these products for any one temperature were 

 constant, the density of the steam was constant, viz : the 

 theoretical density, 9, the weight could be ascertained by the 

 equation 



_ Vapor density X p> vX 273 

 ~"1 1-1636 X 1000 X 760 X (273+ t)' 

 This expression simplifies to 



log W = \ogp. v + 4-46179— log (273 -M). 



" During the progress of the experiments it happened that 

 a trace of water passed up the tube, adding itself to that 

 already present. This, of course, increased the weight, hence 

 new measurements were made to determine the amount of the 

 increase." 



Thus were made the determinations of the weight of water 

 in the tube, one the mean of experiments where the tempera- 

 tures were 220° and 230°, the pressures ranging from 2500 mm 

 to 3800, in the second the temperatures were 230°, 240° and 

 250°, the pressures ranging from 2600 to 4000, and in the third 

 the temperatures were 250°, 260°, and 270°, the pressures 

 ranging from 2800 to 4300. Now evidently at such pressures 

 and volumes (the greatest specific volume came out 0*676) it is 

 impossible that the steam can be in the condition of a perfect 

 gas, and accordingly the determination of the weight in each 

 of the three series is incorrect, and the volumes given by Ram- 

 say and Young should be diminished. The errors in the three 

 sets are probably very close to the same amount, for although 

 the increase in temperature would mean a decrease in the error 

 due to the assumption that the steam comported itself as a per- 

 fect gas, nevertheless the specific volumes in the three sets 

 used for the determination of the weight diminished enough 

 to offset this. 



Assuming then this constant error in Ramsay and Young's 

 determinations, let us make a comparison of such of them as 



