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

178 METAL-AMMONIA COMPOUNDS.

number of times, and, after it has stood for 24 hours, filter off the
slime of hydrated manganese dioxide. Neutralize the nitrate with

dilute hydrochloric acid, and, while keeping it cold by surround-

ing the vessel with ice, precipitate the product by the gradual

addition of a mixture of three volumes of concentrated hydro-
chloric acid and one volume of alcohol. Wash the precipitate

with alcohol. Yield, 12 to 15 grams.

3. Purification of Aquopentamminecobaltic Chloride. Dissolve

the crude product, prepared according to either 1 or 2, in cold,

2% ammonia, using 75 c.c. for each 10 g. of the salt; filter off the

slight residue of luteo salt, and, while keeping the solution cold
with ice, precipitate the roseo salt by the gradual addition of con-

centrated hydrochloric acid. Drain the precipitate and wash

it with a mixture of equal parts concentrated hydrochloric acid

and water, then with alcohol, and dry it in a warm place.

4. Aquopentamminecobaltic Oxalate. Dissolve 10 g. of chloro-

pentamminecobaltic chloride in a flask with 75 c.c. of water and
50 c.c. of 10% ammonia, heating on the water-bath. After cool-

ing the deep-red solution to the room temperature, filter it and

treat with a solution of oxalic acid until a precipitate begins to

form, then continue to add the reagent very carefully until the
solution is just acid. Filter, and wash the salt with water.

To purify the product, dissolve it as directed under 3, and re-

precipitate the salt by the careful addition of oxalic acid solution.

Drain the precipitate, wash it with water, then with alcohol, and

dry it in a warm place. Yield, 9 grams of pure

1

substance.

5. Aquopentamminecobaltic Chloride from Aquopentammineco-

baltic Oxalate. Cover 10 g. of aquopentamminecobaltic oxalate

at room temperature with 30 c.c. of water and dissolve the salt by
the addition of 50 c.c. of normal hydrochloric acid. Cool the solu-

tion with ice to about 0° and precipitate it very slowly by allow-

ing 100 c.c. of concentrated hydrochloric acid to flow upon it

drop by drop. Drain off the bright red precipitate and wash it

first with hydrochloric acid diluted to one-half and then with

alcohol. Yield, about 8 g. of perfectly pure aquopentammineco-

baltic chloride.

(^1) The separation of luteo salt present as impurity is here more complete
than according to procedure 3, because its oxalate is much more insoluble
than its chloride.