296 RTESSRS. THORPE AND MORTON ON THE 



which we have employed in the determination of the amount 

 of bromine contained in the water of the Irish Sea. This 

 method has been carefully studied by Fehling, and we have 

 therefore followed the directions given by that chemist in 

 his memoir^. To the measured quantity of sea- water, in 

 each case a litre, weighing 1027 grms., a small quantity 

 of solution of silver nitrate was added (about -2V of that re- 

 quired to effect complete precipitation), and the liquid re- 

 peatedly shaken for eight days. The precipitates were 

 then collected,, thoroughly washed, dried, and weighed. 



Water taken. Amount of mixed 



grms. silver salts. 



1 1027 2*85068 



II 1027 2'31020 



The mixed silver salts were then transferred to porcelain 

 boats, and heated in a stream of pure hydrogen until they 

 ceased to lose weight. All the weighings were made by 

 the method of vibrations, as described by Bunsenf. By 

 this means a difference of one-hundredth of a milligram 

 is easily detected. 



Amount of AgCl Ag Equivalent to On the original 



and AgBr taken. obtained. -A-gCl. amount, 



grms. gi'm. grms. grms. 



3-39584 178195 2"3679o 2-81736 



2-1 1510 1-56640 2-08148 2-27347 



Hence the amount of AgBr is 



Bromine in 1000 grms. 



1 0-14029 0-05827 



II 0-15501 0-06438 



Mean 0-06133 



The presence of iodine in sea-water has not been con- 

 clusively demonstrated. Its existence in the water has 

 simply been inferred from the fact of its being contained in 



* Journ. f. prakt. Chem. xlv. 269. 

 t Phil. Mag. 1867, xxxiv. 



