AQUOPENTAMMINECOBALTIC SALTS. 177
dilute nitric acid, filter, and dilute the solution to 100 c.c. Add
200 c.c. of concentrated ammonia, heat the solution to boiling,
and oxidize the salt by adding 25.4 g. of iodine, which must be
introduced slowly at first. A vigorous reaction takes place and a
pale yellowish-brown precipitate of luteo salt is formed. All the
iodine should be added in the course of half an hour. Allow the
liquid to cool and after it has stood about two hours filter off
the precipitate and wash it with water containing ammonia. Then
boil the salt with 200 c.c. of approximately 56% nitric acid, where-
by iodine is set free which can be recovered to some extent by
means of two funnels, one placed in the flask and the other inverted
over it to form a double cone. When all the iodine has been
expelled, filter off the precipitate, drain it with suction, wash it
with water containing nitric acid and finally with alcohol, and dry
it in the hot closet. Yield, about 22 grams.
- Aquopentamminecobaltlc Salts, [Co(NH 3 ) 6 H 2 O]Cl3
(Roseocobalt Salts).
Chloropentamminecobaltic chloride dissolves in ammonia, forming aquo-
pentamminecobaltic chloride. If this solution is precipitated hot with
hydrochloric acid, the chloropentammine salt is formed again, but if the
hydrochloric acid is added slowly and the solution kept very cold, aquopent-
amminecobaltic chloride separates. Less care need be taken in the prepara-
tion of the difficultly-soluble aquopentamminecobaltic oxalate. Aquopent-
ammine salts are also formed by the oxidation of hexamminecobaltous salts
by potassium permanganate. - Dissolve 10 g. of chloropentamminecobaltic chloride in a
liter flask by shaking it with 300 c.c. of 5% ammonia and heating
upon the water-bath. Filter, if necessary, and then cool the solu-
tion to about 0°, first by holding the flask under running water
and then by surrounding it with ice. While rotating the flask and
keeping its contents cold, add strong hydrochloric acid from a
dropping-funnel, a few drops at a time, until the solution reacts
acid. Filter and drain the bright-red, crystalline precipitate;
wash it first with a little 50% alcohol then with pure alcohol and
dry it in a fairly warm place. Yield, 10 grams.- To a cold solution of 20 g. crystallized cobaltous chloride
in 360 c.c. of water, contained in a 1500 c.c. flask, add 110 c.c. of
concentrated ammonia and then 10 g. of potassium perman-
ganate dissolved in 400 c.c. of water. Shake the mixture a