loduret and Hydriodate of Iron. 307 
given strength, and place in it two or three doubles of clean 
soft iron wire, sufficiently long to extend to the surface of the 
fluid ; boil it for a few minutes, and then leave it at rest until 
the solution becomes clear, after which it may be either de- 
canted off from the precipitate which forms, or filtered : no 
farther change takes place in a solution thus treated if it be 
kept in a blackened or a green bottle, however long it may 
be preserved. In this process, the wire affords iron to satu- 
rate any free iodine present in the solution, or that may have 
been extricated by the formation of the peroxide of iron in 
the ioduret ; and a perfectly neutral solution being thus ob- 
tained, by the immediate conversion of the new formed ioduret 
into the hydriodate of the protoxide, no subsequent change 
takes place so long as the solution is kept secluded from the 
light. It is not easy to explain this influence of light in de- 
composing the solution of the hydriodate of iron ; but several 
others of the metallic hydriodates are affected in the same 
manner by light. The best proportions for forming the medi- 
cinal solution are three grains of the dry solid ioduret to 
each fluid drachm of distilled water. If the water be not 
either distilled, or filtered rain water, perfectly free from 
foreign ingredients, particularly if it contain any earthy or 
saline carbonates, decomposition instantly takes place, iodine 
is extricated, and a carbonate of iron, which rapidly passes 
into the state of the peroxide of that metal, is precipitated. 
Physiological Effects of Hydriodate of Iron. — " When taken 
in doses of from three to five grains, the hydriodate of iron 
makes no sensible impression on the stomach, although it 
sharpens the appetite and improves the digestive function; it 
seems to stimulate moderately the intestinal canal through its 
entire length, as it opens the bowels ; and whilst it produces 
the black color of the alvine discharges characteristic of all 
the preparations of iron, it corrects their fcetor. When it 
does not affect the bowels, it augments the action of the 
kidneys, increasing the flow of urine ; and if the solution be 
taken two or three times a-day, for several days successively, 
the presence of both the iodine and the iron can be readily 
