EVAPORATION 



327 



RATE OF EVAPORATION IN A QUADRUPLE EFFECT AS INFLUENCED BY " PRESSURE " 

 OF STEAM IN FIRST CALANDRIA. 



Analysis of the results in the two preceding schedules leads to the follow- 

 ing conclusions : 



1. The value of K increases as the temperature difference increases, 

 although certain observations present irregularities, probably due to errors 

 of experiment and to difficulty in maintaining all desired conditions 

 unchanged. 



2. In the series with C 1 constant and FS 4 varying, the value of K m 

 does not surfer much change, so that the water evaporated is nearly directly 

 proportional to the total temperature difference, or to C l FS 4 . 



3. Comparisons of values of K are obscured by the effect of the variation 

 in the absolute value of the temperature difference, and by its position in 

 the absolute scale of temperature ; thus in the series with Cj constant, 

 K l regularly increases as C l C 2 increases, and K remains fairly constant 

 with a slight increase in the same sense. The less values of K occur when 

 C 4 FS 4 is smaller, but higher in the absolute scale of temperature. These 

 two influences may counterbalance each other, so that the combined effect 

 on K is small. On the other hand, in the series with C x varying and FS 4 

 designed to be constant (actually, however, with a variation of 6 F.) there is 

 small change in the value of K lt with, if anything, a tendency to increase 

 as C l C 2 increases. K^, however, increases very largely, and here increase 

 in the value of C l -- F5 4 is accompanied by an elevation of the position of 

 C x F5 4 in the absolute scale of temperature ; at the same time a very 

 material increase occurs in the value of K m . 



4. Increasing the temperature difference (C l -- FS 4 ) by increasing the 

 temperature at the hot end (increase of C t or increase in the pressure of the 

 heating steam), increases the value of K m or the capacity of the apparatus 

 much more than in direct proportion to the value of C l FS 4 . Increasing 



