172 On Steam and Brines 



of W z in the cases where / A is not more than o'i to o 3 C. 

 When this difference is larger, then the passage of steam has 

 not been interrupted until all the salt has disappeared. This 

 is the preferable practice. When any solid salt is present, 

 and the temperature has fallen below the maximum, we know 

 exactly the temperature of the boiling brine and the weight 

 of water in it, but as there is an uncertain proportion of the 

 salt originally taken which has not passed into solution, the 

 concentration or dilution of the brine is uncertain. For this 

 reason it has been impossible in the majority of cases to 

 use /! and W l in the computation of W . The values of W 

 have been arrived at in the following way : The difference 

 W* (t-7\- W 3 (t - T) 3 is found, also the differences / 2 - /, and 

 4 >, then we assume that 



and this value divided by (f T} gives W . Thus in ex- 

 periment No. i on 0*2 KC1, when T= ioo'44 C., we have 

 W z (t- T\= 217-6, and W a (t-T\=2i 2-9, their difference being 

 47. Also 4 4 = o-8i C., and t 2 t 3 = ix)5 C, whence we 

 have W (t - T\ = Jfa 47 + 2 1 7-6 = 2 2O'6, 



whence W = 26-30. 



It will be seen that the value of W^ is 25-91, and /j- T=8-2%, 

 only o-ii C. below 4 T. The passage of steam had there- 

 fore been stopped too soon ; there was solid KC1 present in 

 greater quantity than could in any length of time be dissolved 

 in the amount of water present. Again, if we look at ex- 

 periment No. 4, we find the observed value of W l} 27-25, 

 almost identical with the computed value of W , 27-21. Here 

 the difference, 4 ^, is o'2 C. So that, working in the way 

 described, with chloride of potassium, when the temperature 

 of condensation of the steam has fallen by o'2 C., we should 

 expect to have the amounts of free water and free salt present 

 in compensating amounts. No. 6 represents a case in which 

 the steam was passed until all the salt was dissolved, and until 

 the temperature of condensation had fallen by a whole degree. 

 Here we use W,(t - 7^ and W*(t- T). 2 for finding W 9 (t- T\ 



