Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

TRINITRITOTRIAMMINECOBALT. 183

12 hours more and then collect the precipitate on a filter. The

chloroaquotetrammine salt is very similar externally to the chloro-

purpureo salt, but differs from it in the following reactions:

mercuric chloride gives well-formed crystals only after standing

for some time; potassium chromate and dichromate likewise

yield precipitates only after long standing, or not at all.

B. Distinguishing Reactions. Boil small portions of the salts,

each with 1 c.c. of concentrated hydrochloric acid. The flavo salt

gives a green precipitate of praseo salt and the solution acquires a

bluish color. The croceo salt, on the other hand, gives a dull-red

precipitate of chloronitritotetramminecobaltic chloride.

To prepare somewhat larger amounts of these last substances,

dissolve 0.5 g. of the flavo or croceo salt in 10 c.c. of concentrated

hydrochloric acid. After 12 hours filter, drain and wash the

precipitate, first with hydrochloric acid diluted with an equal

volume of water, and finally with alcohol. Yield, 0.4 g. of each.

The chloronitritotetramminecobaltic salt dissolves readily in 35 c.c.
of cold water and recrystallizes upon the addition of 70 c.c. of

concentrated hydrochloric acid to the filtrate. The praseo salt,

which decomposes very easily, can be recrystallized by dissolv-

ing it quickly in about 200 c.c. of cold water, cooling the filtrate
with ice and salt, and slowly introducing 70 c.c. of concentrated

hydrochloric acid.

139. Trinitritotriamminecobalt, [Co(NH,) 3 (NOs)8].
     Dissolve 45 g. of crystallized cobalt chloride in 125 c.c. of water.

Dissolve 50 g. of ammonium chloride and 67 g. of sodium nitrite

without heating in 375 c.c. of water and add this, together with 250
c.c. of 20% ammonia, to the first solution. Conduct a rapid cur-

rent of air through the mixture for four hours (cf. No. 108). Divide

the thick brown solution in three evaporating dishes and allow it

to stand three days in the open air or under the hood. Filter off
the crystals which separate and wash them with cold water until

the washings are nearly free from chloride. Yield, about 35 g.

Divide the crude product between two filters and extract it with
1.0 to 1.25 liters of hot water containing a little acetic acid. On
cooling, yellow to yellowish-brown crystals of trinitritotriammine-

cobalt separate from the clear filtrate. Yield, 20 to 25 g.

Solutions of this substance do not conduct the electric current