HEXAMMINECOBALTIC SALTS. 175Dissolve it in a little warm water, cool the solution and precipitate
the nitrate by adding concentrated nitric acid (Mass-action).
Recrystallize in order to obtain a purer product. Small dull-red
crystals.
Reactions. The aqueous solution of the pure sulphate gives no pre-
cipitate when treated with silver nitrate at the room temperature;'
on heating, however, some silver chloride is thrown down, but even
on boiling, the reaction is incomplete. On the other hand, the
sulphate radical, not being contained in the complex, gives at
once a quantitative precipitation with barium chloride. The
nitrate shows a similar behavior towards silver ions; the solution
becomes turbid only on boiling.
In the analysis of the salt, chlorine and sulphate are determined
after the substance has been decomposed by boiling with caustic
soda; cobalt is weighed as sulphate after igniting the salt and
heating the residue with concentrated sulphuric acid; ammonia
is estimated in the usual manner by distilling with caustic soda
and titrating the distillate.
- Hexamm}necobaltlc Salts, [Co(NH 3 ) 6 ]X 3 (Luteocobalt Salts).
la. Luteocobalt Chloride. Place 10 g. of chloropentammine-
cobaltic chloride, 8 g. of ammonium chloride, and 100 c.c. of 20%
ammonia solution in a soda-water bottle (pressure-flask), and
stopper it tightly. Wrap the bottle firmly in a towel, fasten it to
a wooden handle and heat it for six hours in a pail of boiling water,
shaking thoroughly once every two hours. Since a strong pres-
sure prevails in the bottle, this part of the process should be
carried out outside of the general laboratory, and before each
shaking- the mixture should be removed from the bath and allowed
to cool somewhat. At the end of the heating the chloropent-
ammine salt must have disappeared almost entirely. When cold
open the bottle, pour the contents into an evaporating dish, and
let it stand 24 hours in the open air, or under the hood, to allow
the ammonia to volatilize. Dilute with 300 to 400 c.c. of water,
add 50 c.c. of concentrated hydrochloric acid and heat the mixture
in a flask for an hour on the water-bath. Add 250 c.c. more of
concentrated hydrochloric acid and cool rapidly, while shaking,under the water-tap. Drain the yellow precipitate on a hardened
filter paper and wash it with 20% hydrochloric acid,