Identification—
A:
To 2 mL of Syrup add 5 mL of 3 N hydrochloric acid, then add, with stirring, 1 mL of sodium nitrite solution (1 in 2). Chill in an ice bath for 15 minutes, stirring if necessary, to induce crystallization, filter the precipitate on a sintered-glass funnel, wash with 10 mL of cold water, and dry at 105
: the
N,
N¢-dinitrosopiperazine so obtained melts between 156
and 160
.
B:
It responds to the tests for
Citrate 
191
.
Assay—
Determine the specific gravity of Syrup, and transfer an accurately weighed portion of the Syrup, equivalent to about 200 mg of piperazine citrate, to a 250-mL beaker. Add 10 mL of water and 75 mL of trinitrophenol TS, stir well, and allow to stand in a refrigerator for not less than 2 hours. Collect the precipitate in a tared filtering crucible, wash with five 10-mL portions of dehydrated alcohol, and dry at 105
to constant weight.
[Caution—Picrates may explode.] The weight of the dipicrate, multiplied by 0.3568, gives the equivalent of C
4H
10N
2·6H
2O in the portion of Syrup taken.
