ON IODIDE OP POTASSIUM. 
291 
bonate, and as there is an excess of the iodide of iron, a 
white precipitate is immediately produced. We now agi- 
tate the flask briskly, to mix the solutions thoroughly, and 
likewise that the heavy sediment may envelope the very 
light precipitate last produced, and carry it down quickly, 
so as to leave the liquid clear, otherwise the liquid would 
remain thick and cloudy for a very long time. 
By proceeding as directed, the liquid in a few minutes be- 
comes quite transparent; we then add more alkaline solu- 
tion, and proceed as before. We continue adding the solu- 
tion, but more cautiously towards the end, till no reaction is 
produced on a fresh addition. 
After complete subsidence of the sediment, we pour off 
the liquid into an evaporating bason, and press the precipi- 
tate strongly in a cloth; we then break up the mass in about 
six ounces of distilled water, press again, and add the liquids 
to that already in the basin, and evaporate till near the point 
of crystallization. 
We may here*remark, that we prefer pressing through a 
cloth, to the tedious process usually recommended of wash- 
ing the precipitate on a filter, with an abundance of water, 
till every trace of iodide be removed from it, and thus in- 
creasing unnecessarily, and to a large amount, the quantity 
of liquid to be evaporated; and we feel persuaded that we 
will be supported in our view of this matter by every prac- 
tical man, and for the following reason: 
After pressing strongly the precipitate, there is not at the 
most more than an ounce of liquid left; and as the whole 
amount of the liquid was six pints, or 120 oz., and contained 
in solution'11.8 oz., or 5664 grains, of iodide, there could 
only be the l-120th of that quantity in what was left, that 
is 47 grains; but as the precipitate was diffused through six 
oz. of water, the whole seven oz. would contain no more 
than 47 grains; and, on again pressing, only the seventh 
part would be left behind, which is somewhat less than 
seven grains. 
