13 Analysis of Sea Water. 



Art. II. — Analysis of Sea Water as it exists in the English 

 Channel near Brighton ; hy G. Schweitzer, M. D.* 



Being unaware of the existence of a correct analysis of sea- 

 water as it exists in the British Channel, particularly with refer- 

 ence to the quantity of iodine and bromine it contains, I have 

 undertaken at the request of several friends to analyze it. It is 

 not my intention to enter into the minutise of the process em- 

 ployed, particularly as I have on a former occasion, in a small 

 pamphlet entitled " An Analysis of the Congress Spring of Sara- 

 toga in America," published in March, 1838, given a detailed 

 account of the mode I adopt in analyzing mineral waters. The 

 chief object I have in view in the present communication is, to 

 explain the method I have employed in ascertaining the propor- 

 tion of iodine and bromine contained in a given quantity of sea- 

 water. Bat before I enter upon the subject, it may not be out of 

 place to show how far tests act upon iodine when in connexion 

 with an alkali, and in a solution also containing bromides and 

 chlorides. 



From experiment I have ascertained that a minute quantity of 

 iodine in distilled water, equal to no more than 1,500,000th part 

 of the whole, will be distinctly indicated when mixed with 

 starch, dilute sulphuric acid, and chlorine. 



For the production of such delicate reaction, I add to every 

 500 grains of fluid one drop of diluted sulphuric acid, a small 

 quantity of paste of potato starch, and two drops of a weak so- 

 lution of chlorine, consisting of one part of a saturated solution 

 diluted with 20 to 25 times its volume of distilled water. The 

 solution gives no indication of the presence of iodine in the fluid 

 until a sufficient time has been allowed for the separation of the 

 starch, when a decided pink hue will be visible on the surface of 

 the precipitate if iodine be present. It has been supposed that 

 the substitution of pink for blue in the iodide of starch produced, 

 arises from the presence of bromine ; but this I have ascertained 

 is not correct, as it depends entirely on the minute quantity of 

 the precipitate acted upon by free chlorine or bromine. The fol- 

 lowing experiment will prove this fact. In order to ascertain the 



* From the Lond. and Ed. Phil. Mag. for July, 1839; communicated by the 

 Author. 



