WATER OF THE IRISH SEA. 295 



VII. Determination of the Potash and Soda contained in 

 the mixed Chlorides. 



Probably none of the processes employed in the analysis 

 of sea-water is so unsatisfactory as that generally used in 

 the determination of the amount of sodium and potassium. 

 The quantity of the latter element contained in sea-water 

 is relatively very small ; and the loss of potash in the ordi- 

 nary method of separation, as the platinum salt, amounts, 

 even under the most favourable circumstances, to upwards 

 of one per cent. The difficulty in applying this method 

 for this purpose has already been pointed out by Usiglio"^ 

 in his " Memoir on the Composition of the Water of the 

 Mediterranean." We have preferred, therefore, to deter- 

 mine the proportion of potash and soda contained in the 

 mixed chlorides by the indirect method of estimating the 

 amount of chlorine present in the mixture, and calcu- 

 lating from this the proportion of the two alkalies. This 

 manner of proceeding is certainly more expeditious, and, 

 we believe, if conducted with due care, quite as accurate 

 as the other method. 





Mixed 

 clilorides. 



AgCl 

 obtained. 



NaCl. 



KCl. 



In 1000 grms. 

 Na. K. 



I. 



... 1-3875 



3-3848 



1-3492 



0-0383 



10-3890 "39300 



II. 



... 1*3920 



3-3957 



1-3540 



0-0380 



10-4150 '38963 



Means 10-4020 0-39131 



VIII. Determination of the Bromine. 



When silver nitrate is added to a cold solution of the 

 alkaline bromides and chlorides, in quantity insufficient 

 to precipitate the whole of the halogens, and the mixture 

 of the silver salts allowed to remain in contact with the 

 liquid for a few days, the whole of the bromine is removed 

 from the solution, and is contained in the precipitate as 

 silver bromide. Upon this principle is based the method 



* Ann. de Chimie, ser. 3. xxvii. 104. 



