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

172 METAL-AMMONIA COMPOUNDS.

theoretical. If desired the preparation can be carried out on a

smaller scale.

139. Carbonatotetramminecobaltic Nitrate,
     [C0(NH 3 ) 4 CO 3 ]NO 3 -JH20.
     When cobalt salts are treated out of contact with the air with an excess of
     ammonia, hexamminecobaltous salts are formed. If such a solution is mixed
     with a large amount of ammonium carbonate, oxidized by the air, and then
     evaporated to a small volume with the addition of more ammonium carbonate,
     crystals of carbonatotetramminecobaltic salt are produced.
     Dissolve 20 g. of cobalt carbonate in as. little concentrated
     nitric acid as possible and dilute the solution to 100 c.c. (or 50 g.
     of crystallized cobaltous nitrate may be dissolved in an equal
     amount of water).
     Dissolve 100 g. of ammonium carbonate in 500 c.c. of water in
     a 1-liter flask, add 250 c.c. of concentrated ammonia, and into
     this solution pour the above prepared solution of cobalt nitrate.
     Draw a stream of air through the deep-violet-colored liquid in the
     manner described under No. 108. At the end of three hours,
     pour the liquid, which is now of a blood-red color, into a porce-
     lain evaporating dish, and concentrate it to about 300 c.c, adding
     5 g. of powdered ammonium carbonate every fifteen minutes
     (about 25 or 30 grams in all). Filter the solution immediately

from any small amount of sediment and boil it down to 200 c.c,

still continuing to add ammonium carbonate in small quantities

(about 10 g. in all during this final evaporation). Allow the

liquid to cool and collect the large, purple crystal-plates which

separate out. Wash the crystals with a little water, then with

dilute alcohol and finally with pure alcohol. Recover a crop of

impure crystals by concentrating the mother-liquor; extract this
product at the laboratory temperature with 15 times its weight

of water, and precipitate the salt from the filtered solution by

gradually adding two to three volumes of alcohol. Collect this

precipitate and wash it as directed above. Total yield, 22 to
25 grams.

130. Chloropentamminecobaltic Chloride, [Co(NH 3 ) 6 Cl]Cl 2 ,
     from the preceding.
     The preparation of chloropentamminecobaltic chloride from the carbonato-
     tetrammine salt is an example of the replacement of certain constituents
     in the complex by means of others. On acidifying an aqueous solution of