14 Analysis of Sea Water. 
The iodide of starch will likewise keep unchanged much longer 
in a solution of chlorides exposed to light and air than in pure 
water. 
The bromides when present in large quantity interfere with 
the delicate reaction upon traces of iodine, but when the quan- 
tity of iodine is not too small the reaction is very distinct, as a 
small proportion of free bromine will, like chlorine, decompose 
the iodide, and produce the slnaciadtescinede reaction. 
_ After these experiments I tested fresh sea-water for idatowd in * 
the manner before described, but did not obtain the slightest in- 
dication of it. Inow added one millionth part of the iodide of 
potassium, and the color produced by the test did not differ in ~ 
the slightest degree from a solution of chlorides of the same spe- 
cific gravity as sea-water, treated in the same manner, and from 
this I immediately inferred, that iodine, if pera. in sea-water, 
must be so in very minute quantity. 
I took 73 pounds troy of sea-water, and boiled with a quan- 
tity of caustic potash, sufficient to precipitate the alkaline earth, 
and after filtration evaporated the fluid to four ounces. On test- 
ing a small quantity of this concentrated water, no iodine was to 
be detected, and it was found on adding a minute quantity of an 
iodide that the presence of bromides in comparatively large quan- 
tity interfered with the test. But although these results appear- 
ed to negative the presence of iodine, I felt convinced it must 
exist in sea-water, being present in so many sea plants and 
animals. 
Sarphate, in his “ Commentatio de Iodio,” 1835, Leiden (a 
. treatise which received the prize), states that he could detect no 
¥. 
; 
iodine in the sea-water near the Dutch coast. Professor Charles 
Daubeny likewise mentions, in his “ Memoir on the occurrence 
of iodine and bromine in certain mineral waters of South Brit- 
ain, May, 1838,” that he could not detect iodine in the residuum 
of sea-water taken from the English Channel near Cowes, after 
having reduced ten gallons to less than half an ounce. 
To proceed with my experiment, I freed three ounces as much 
as possible from the chlorides by crystallization, having first care- 
fully neutralized the a eoliition, with hydrochloric acid. The re- 
duu | raporated to dryness, ignited, and treated with 
alecholic 
fluid was afterwards evapo- 
ssolved in a few drams of water; 
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bE a ty ade 
