174 n Steam and Brines 



like the law connecting the volume and pressure of a gas at 

 constant temperature. If we look over Table IV we see that 

 for some salts, and mixtures of salts, the values of W(t- T} 

 are very nearly quite constant, while for the others, some 

 deviate from constancy in the one sense, and some in the 

 other. In the case of the chlorides of potassium and of 

 sodium, the values of W(t T) diminish very considerably 

 as the value of W increases. The case of ammonium chloride 

 is peculiar, because at the sea-level W (t T) diminishes as 

 W increases ; at a height of 3000 metres it increases with W, 

 and at a height of 2000 metres it is sensibly constant. In the 

 case of barium chloride, W(t T) diminishes with dilution ; 

 the same is the case with strontium nitrate and ammonium 

 sulphate. Potassium chlorate, barium nitrate, and lead nitrate 

 show W(t T} increasing with W, while sodium nitrate and 

 potassium sulphate show almost constant values of W (t T). 

 Mixtures of salts follow the rule of their components. There 

 are several examples in the table of pairs of salts which 

 individually differ in the sense in which the values of W(t T] 

 depart from constancy, and in mixture give constant values 

 of W(t T}. Examples are Nos. 63, 70, 71, 72, 73, 78, 

 and 79. 



At the beginning of an experiment, when the steam reaches 

 the salt, it condenses very rapidly owing to abstraction of 

 heat by the glass and by the salt, then it condenses at a very 

 regular rate, the salt dissolving in proportion as steam is con- 

 densed. After a certain time the exact amount of steam has 

 condensed which is necessary to form a boiling saturated 

 solution of the salt taken ; having observed (/ T] and W 

 we have the value of W (t - T}. If the elevation of the boiling 

 point were proportional to the concentration, the factor 

 W(t T] would remain constant while the solution was 

 diluted by further condensation of steam. But if we deny 

 thermal importance to the salt and consider only the water, 

 then W (t Q T} is the heat in the boiling saturated water, 

 counting from the temperature of pure boiling water. If we 

 prevent it from losing heat, and provide for dilution by furnish- 

 ing water of exactly the temperature of pure steam condensing 



