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

170 METAL-AMMONIA COMPOUNDS.

dissolve the perfectly dry residue in the least amount possible of

concentrated ammonia (Hood). Filter the solution and allow it

to crystallize. Recrystallize the crude product from water con-

taining a little ammonia. Yield, about 5 grams of colorless,

columnar crystals.

Analyze the product by determining the silver as AgCl and the

ammonia by distilling with caustic soda and titrating the distillate.

136. Tetramminecupric Sulphate, [Cu(NH 3 ) 4 ]SO 4 -H 2 O, and Ammonium
     Cupric Sulphate, CuSO 4 -(]VH 4 )2SO 4 -6 H 2 O.
     The first of these salts may be regarded as ordinary blue vitriol in which
     four molecules of water have been replaced by ammonia. The fifth mole-
     cule of water evidently has another function from that of the other four,
     cf. p. 191 (top).

Dissolve 20 g. of powdered blue vitriol in a mixture of 30 c.c.

concentrated ammonia and 20 c.c. of water and precipitate the

deep-blue solution (first filtering it through asbestos if necessary)

by the gradual addition of 30 c.c. alcohol. After standing for

some hours in the cold, filter off the dark-blue crystals with suc-

tion, and wash them first with a mixture of equal volumes of

alcohol and concentrated ammonia and finally with alcohol and

ether. Dry the salt at the laboratory temperature. Yield, almost

quantitative.

Ammonium Cupric Sulphate crystallizes on cooling from a hot

solution of 25 g. blue vitriol and 13.25 g. ammonium sulphate

in 40 c.c. of water. Recover the last portions of the salt by con-

centrating the mother-liquor. The yield is nearly quantitative,

and consists of large, light-blue crystals. The aqueous solution

of the salt gives a precipitate of cupric hydroxide on being treated

with sodium hydroxide. The salt belongs to the large class of

monoclinic double salts which crystallize with six molecules of

water.

127. Tetramminecupric Chloride, [Cu(NH 3 )JCl2-H 2 O.
     In order to prepare this salt, which is readily soluble in water,

conduct ammonia gas through a wide delivery tube into a warm
filtered solution of 17 g. crystallized cupric chloride in 15 c.c. of

water. The ammonia gas is obtained by heating 100 c.c. of con-

centrated ammonia solution gently and passing the gas through

an empty wash-bottle to free it to some extent from water vapor.