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SELECTED ARTICLES. 
and 5° C. During this solidification, its color was deepened, 
and became of a blue black. Exposed in this solid state to 
the open air for a night of January, during which the ther- 
mometer fell to — 10° or 1 1° R. the congealed mass, under the 
influence of this cooling, had acquired a yellowish brown co- 
lor, which it retained at 10°, and lost gradually as the tempera- 
ture rose, repassing to a deep blue; placed in a warm cham- 
ber, it liquified by little and little, and during its change of 
state, there was a separation of the iodide of amidine from 
the water; for this latter was no longer colored, and the iodide 
was deposited, in the form of blue flocculi, at the bottom of the 
vessel. 
This freezing of the iodide of amidine by the action of cold, 
and its separation from the water which held it in solution 
previous to its congelation, can be attributed, in our opinion, 
only to the cohesion which had taken place between the mole- 
cules of this compound, which cohesion had modified its affi- 
nity for the water. In fact, we have proven that by gradually 
heating this aqueous liquor in which the iodide was only in 
suspension, and not dissolved, the water, by an elevation of 
temperature of +55° to 60°, became colored of a fine blue by 
redissolving it, and then presented all the characters of a solu- 
tion colored and permanent even at common temperatures, 
with the properties which the blue solution of iodide of ami- 
dine, possessed before its congelation. 
This observation, joined to the former, does not permit us 
to doubt of the reality of the solubility of the iodide of ami- 
dine in water at common temperatures, but that it evidently 
separates when a physical force tends to unite its molecules, or 
when a chemical action determines its union with other bo- 
dies which then renders it insoluble in water. 
We eannot pass over in silence a curious observation, which 
we have likewise made upon the solution of amidine prepared 
for four years, and which is not presented by the amidine so- 
lution recently prepared as a point of comparison; it is the 
change of color which takes place in the former solution 
when congealed and exposed to the temperature of — 10°; the 
