194 
ON IMPORTATIONS OF IODINE. 
with in the sepia, or cuttle-fish, the sponge, (whose ashes 
yield iodide of sodium,) the oyster, in the liver 01 the cod- 
fish and it is believed of several other species of fish, and 
in a singular insect found in Italy. 
While the marine animals and plants containing iodine 
evidently derive this substance from the ocean, it is remar- 
kable that the quantity discoverable in sea-water, is exceed- 
ingly minute, the most careful chemical analysis exhibiting 
a mere trace of it: so that there must exist very peculiar 
powers of absorption or secretion in these plants and 
animals to enable them to obtain an appreciable amount; 
unless iodine should prove to be a compound substance. 
It is from the sea-weeds alone, that iodine can be profitably 
extracted; and even from those varieties, which yield most, 
(perhaps ten times as much as more ordinary varieties,) the 
product is very small, the " kelp" or fused ashes of the 
weed constituting a slight proportion of the original plant, 
and this yielding on an average considerably less than a 
half per cent, of iodine. 
It may be incidentally mentioned as a striking instance of 
the new directions given to industrial enterprise by the dis- 
coveries of science, that this kelp was formerly obtained 
solely for the carbonate of soda it yielded, (ranging from 2 
to 5 per cent.,) while it is now chiefly valued for its iodine, 
and chloride of potassium. These two substances appear, 
as Mr. Whitelaw (a manufacturer in Glasgow) has stated, 
to observe a tolerably uniform ratio of quantity to each 
oihcr, the kelp containing the most chloride of potassium, 
containing at the same time the most iodine. 
The process of subliming the iodine from the aqueous 
solution of kelp is described in the U. S. Dispensatory, and 
more fully in Graham's Chemistry, and in Pereira's Materia 
Medica, and need not here be quoted. The British iodine 
is the only kind that has been imported into Philadelphia 
for the last two years, or since the recent drug law has 
been in operation. During this time there has been no 
