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Analysis of Sea Water. 15 
when the before-mentioned test readily indicated a slight trace 
of iodine. 
With respect to the quantity of iodine in sea-water, it is evi- 
dently very minute, 174 pounds troy not containing one grain. 
This is remarkable when we consider the comparatively large 
quantity of iodine and bromine present in sea plants and animals, 
hence we must conclude that these principles are conemniigie 
"_ by vital action. 
ine, when present in fluids, j is easily detected by chléring, ‘ 
which produces a yellow color. If present in very minute quan- 
tity the fluid must first be concentrated. But when iodine is 
present we cannot apply this test, as bromides and iodides are 
_ both decomposed by it; and we cannot separate them, even by 
means of ether, as iodine is soluble in that menstruum, and also 
"possesses greater coloring properties than bromine. From these 
causes this test is useless when iodine is present, and is only cer- 
tain when we are previously assured of the absence of that sub- 
stance. 
The following process for the separation of iodine, chlorine, 
and bromine in fluids containing these substances in very small 
quantities has given me satisfactory results, as I had anticipated 
by previous experiment. The fluid while boiling was mixed 
with a sufficient proportion of caustic potash ; my object in this 
was to decompose the earthy salts, and at the same time prevent 
the iodine and bromine from being dissipated by heat. The fil- 
tered fluid was then evaporated to dryness and ignited, and the 
resulting mass, after having been dissolved, concentrated, and 
neutralized with hydrochloric acid, was carefully mixed, drop 
by drop, with an ammoniacal solution of chloride of silver pre- 
ared by mixing one part of a saturated solution of recently pre- 
cipitated chloride of silver in ammonia with one of liquid am- 
monia (sp. grav. 0-935) and two parts of water. If to a concen- 
trated solution of chloride of sodium containing one thirtieth 
part of a bromide, we add a few drops of this ammoniacal solu- 
tion of chloride of silver, the solution will remain clear ; but if 
the most minute particle: of an iodide be present, it will be ren- 
dered turbid. 
To the fluid under examination t paoed grodcally, drop by 
drop, the solution of ammoniacal chloride of silver, leaving time 
between each successive addition eee, pee of iodide of 
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