^56 Dr Fyfe on the Plants frmn 
lichens, but without success. It seemed, therefore, that iodmo 
was confined not only to the class Cryptogamia, but to the 
rine productions of this class. 
The next object was, to ascertain if the marine animals of the 
lower orders could be made to yield iodine. For this purpose, 
the residue of the incineration of oysters was dissolved in water ; 
the solution was evaporated to dryness, and sulphuric acid wast 
added, but without any appearance of iodine. Coral was like- 
wise subjected to a similar trial, and with the same result. I 
however succeeded in procuring it from the common sponge of 
the shops, after burning it, and treating it in the usual way 
As from these experiments, it appeared that iodine was af- 
, forded only by marine productions, it was of consequence to as- 
certain if it could be procured from sea- water itself. With this 
view, I subjected the residue of the evaporation of sea-water, to 
various trials. 
The common method of procuring muriatic acid from the sa- 
line matter of sea-water, by the addition of sulphuric acid, con- 
vinced me, that if this substance contained iodine, it could not 
in this way be got from it. I was therefore obliged to have re- 
course to other means. W^hen sea-water is subjected to galvan- 
ism in a gold cup, a small quantity of a black powder is formed ; 
this, it is supposed by Sir H. Davy, might be a compound of io- 
dine and gold. To ascertain if this was the case, a quantity of 
sea-water concentrated by evaporation, was put into a silver ves- 
sel, attached to one end of a galvanic battery ; a gold wire from 
the other end, was introduced into the fluid. The silver in a 
short time acquired a dark coating, and a minute portion of a 
black powder was formed. This was subjected to the action of 
fused potassa, and then to sulphuric acid, but without any ap- 
pearance of iodine. 
During the preparation of kelp, from which iodine is procur- 
ed, the vegetable matter is subjected to a high temperature. 
Conceiving that, perhaps, the iodine might be a product of the 
combustion, some of the residue of the evaporation of sea^water 
* In the experiments with sponge, the vapour of iodine was given off copiously, 
by the addition of sulphuric acid to the ashes. I repeated these experiments seve- 
ral times, as they were at variance with those of Sir H. Davy, PldU Trans, 1815. 
