On the Nitrates of Iron. 31 
A farther additioft changes the color to a dark red, and if the 
action be continued still longer, a rusty precipitate forms. If we 
stop short of this last point, and add to the product its own bulk 
of nitric acid of sp. gr. 1:43, an abundant crop of erystals will be 
deposited on cooling below 60° F. The same result may be at- 
tained by evaporating the greenish liquid, and adding acid enough 
to insure a considerable excess, before setting the solution aside 
to cool. If the first crystals are brown, they may be purified by 
redissolving in nitric acid, with the aid of a gentle heat, and allow- 
ing again to crystallize. 
The crystals thus obtained, have the form of oblique rhombic 
prisms, which are either colorless or of a delicate lavender color, 
but when dissolved in water, yield a yellowish brown solution. 
They are somewhat deliquescent and very soluble in water; 
while ata temperature below 60° F., a weighed quantity was not 
wholly taken up by over tweuty parts of nitric acid of sp. gr. 1:37. 
At about 117° F., this salt melts into a clear, deep red liquid, 
which in one trial remained fiuid till cooled to 83° F., when the 
heat developed by solidification, quickly raised the thermometer 
to 116°. 
The composition of this substance, as indicated below, affords. 
reasons for supposing that by its admixture with a bicarbonate, 
an intense cold might be produced. Such proved to be the case, 
for when two ounces of the bruised crystals were stirred up with 
one ounce of pulverulent bicarbonate of ammonia, the thermom- 
eter introduced fell from 58° to —5° F. Previous cooling is at- 
tended with an increase of effect. é 
These experiments, being very tangible, would furnish excel- 
lent illustrations of the principles o e 
A small quantity of the melted nitrate kept hot for several 
hours by means of a water bath, yielded a perfectly dry, dark 
brown, deliquescent powder, containing some water and one half 
the original amount of acid. More acid may be expelled by a 
moderate heat, but to drive off the last portions, requires a tem- 
perature approaching to redness. ne j 
he well drained crystals afforded by precipitation with am- 
monia 19-8 p. c. of peroxyd of iron, and 100 grs. boiled with 
carbonate of baryta, gave a liquor which with’ sulphuric acid 
smes rectan- 
erhaps the rectangulaire was a mistake, for in several 
‘ have obtained forms variously modified but all referable to the ob- 
lique rhombic system. In one huge crystal which ha n many months in forming, 
th a view to obtain more light on the subject, have 
y not be altogether uninteresting, and are, I trust, 
