ae he ee ee ne ee, 
M. ©. Lea on Picric Acid. 383 
becomes orange-red, boils up and burns with a feeble deflagration, 
leaving a sooty mark and a loose white ash. 
Pricrate of Alumina.—Hot solutions of chlorid of aluminum and 
icrate of ammonia, placed in a beaker glass and left for several 
ays, give beautiful stellar aggregations of crystals which are 
permanent in the air, and by heating become slightly brown and 
then detonate. By recrystallization only crystalline crusts are 
obtained, which no longer detonate by heating, but only defla- 
grate with a smoky flame. 
_ Picrate of Protoxyd of Manganese.—This beautiful salt, the most 
interesting of all the picrates, is easily formed by dissolving the 
protocarbonate of manganese in hot aqueous picric acid. By spon- 
taneous evaporation large prisms belonging to the rhombic system 
are readily obtained. These prisms exhibits the faces oo Poo ,00 Poo, 
with an intermediate prism face, and the terminal planesOP. The 
face co Poo is sometimes wanting, and no pyramidal faces were 
yellow. 
The picrate of manganese does not appear to be capable of 
forming double salts with soda or ammonia. A crystal heated 
on platinum foil becomes deep red and then instantly deflagrates, 
80 suddenly as to project portions which do not take fire. 
crate of Pr of Iron:—Isomorphous with the manganous 
and cadmic salts, crystallizing in large greenish-yellow prisms 
belonging to the rhombic system, and exhibiting the same faces 
as the manganous salt, viz. : 0 P 00, «oP o with an intermediate 
Prism face, and the terminal planes OP. The face o Po is 
also in this, and the isomorphous cadmium salt, often want- 
Ing. It does not, however, appear to possess the dichromatic 
properties of the picrates of manganese and cadmium, and unless 
oroughly protected from the air, peroxydizes gradually on the 
— hen in solution, however, it is sufficiently ee bas 
be crystallized by taneous evaporation in an open | 
orating inh ; the nates of the ehails. becomes indeed covered 
‘With a film of decomposed salt, but good crystals may be picked 
fi th. | 
