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

180 METAL-AMMONIA COMPOUNDS.

To purify the salt, recrystallize from 25 c.c. of water slightly
acidulated with acetic acid. Collect the light-brown, crystalline

flakes, or prisms, which are obtained, and wash with 50% alco-

hol, then with pure alcohol, and dry at a gentle heat. Yield, 6.5

grams.

Reactions. A cold, saturated solution of flavonitrate (3 g. in
100 c.c. water) gives with potassium chromate a crystalline pre-
cipitate of irregularly indented leaflets which are crossed and

branched at right angles (microscope). With potassium di-

chromate small clusters of fine needles are at once precipitated,

which are inclined towards one another like the branches of a fir
tree.

Flavocobalt Chloride, [CoiNH^iiNO^Cl. Dissolve 1 g. of

flavonitrate in 30 c.c. of water, warming gently; add 2 g. of

ammonium chloride and filter if necessary. Then gradually add
100 c.c. of alcohol to the mixture and after standing 24 hours filter

off the small, deep-yellow crystal leaflets. Wash the product

with dilute alcohol, then with pure alcohol, and dry it in the hot

closet. Yield, 0.9 gram.

137. Dinitritotetramminecobaltic Chloride, [Co(NH 3 ) 4 (NO 2 ) 2 ]C'l
     (Croceocobalt Chloride).
     To a cold, filtered solution of 100 g. ammonium chloride and
     135 g. sodium nitrite in 750 c.c. water, add 150 c.c. of 20% ammo-

nia and 90 g. of cobaltous chloride dissolved in 250 c.c. of water.

Draw air through this solution (cf. No. 108) for four hours, whereby
the color, which is at first a pale, brownish-green, changes to

green with a tinge of yellow, and a precipitate is formed. After

standing for 12 hours filter off this precipitate and wash it with

water until the last washing, on being treated with ammonium
oxalate, stirred, and allowed to stand for some time, shows no

precipitation. To purify the product which still contains some

nitrate, divide it first into portions of 20 grams; then dissolve

each portion in 40 c.c. of hot water containing a little acetic acid,
filter the solution quickly through a plaited filter and immedi-

ately precipitate the salt from the filtrate by adding a solution of

40 g. ammonium chloride. Cool the mixture and after letting it

stand 24 hours, filter off the yellow crystals, wash them with

90% alcohol until the washings barely give a test for chloride,