1 68 On Steam and Brines 



was the only salt experimented with at Eggischorn, Fiesch, 

 and Andermatt, as at that date I intended to confine my 

 observations to chloride of sodium alone. 



TJte salts used in this research are the chlorides of sodium, 

 potassium, ammonium, barium ; the chlorate of potassium ; 

 the nitrates of sodium, barium, strontium, and lead, and the 

 sulphates of potassium and ammonium. These salts were 

 used singly, and also in mixtures of not more than two salts 

 each. The charge of the apparatus was usually one-fifth of 

 a gramme-molecule, but with sparingly soluble salts, such as 

 nitrate of barium or sulphate of potassium, one-tenth and 

 sometimes one-twentieth of a molecule were used. A watch, 

 giving minutes and seconds accurately, was observed during 

 all the experiments. In the case of simple salts the time was 

 noted when the steam reached the salt, when the salt formed 

 a magma, with the steam condensed, when the maximum 

 temperature was reached, when it began to fall, and when the 

 passage of steam was stopped previous to making the first 

 weighing. These particular epochs were always noted, but, 

 as a matter of fact, a complete time-log was kept of every 

 experiment. In experiments with mixtures the temperature 

 was noted every minute, and often every half-minute, so long 

 as salt remained undissolved. A complete time record of this 

 kind often furnishes valuable incidental information, and is 

 often useful in detecting and rectifying errors of observation. 



Chloride of Sodium. The series with this salt is very com- 

 plete, including sixteen independent experiments ; the atmo- 

 spheric pressure varied from 550^4 to 772 mm., and the 

 temperature of saturated steam from 9i'2 C. to ioo'44 C. The 

 corresponding temperatures of the boiling mixture ranged 

 from 99'3C. to io8'98 C., so that the elevation of boiling-point 

 caused by saturation with NaCl ranges from 8'i C. to 8 0- 54 C., 

 or nearly half a degree Centigrade of increase for a rise of 

 boiling-point of the salt solution of 9'68 C. Roughly, it 

 diminishes o'O5 C. for every degree that the boiling tempera- 

 ture of the boiling solution falls. The results of the observa- 

 tions in different localities are collected in Table I, page 186. 



If we consider the relation between atmospheric pressure 



