(C
15H
21N
3O
2)
2·H
2SO
4
648.77
Pyrrolo[2,3-
b]indol-5-ol, 1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethyl-, methylcarbamate (ester), (3a
S-cis)-, sulfate (2:1).
Physostigmine sulfate (2:1)
[
64-47-1].
Packaging and storage—
Preserve in tight, light-resistant containers.
Identification—
B:
A solution (1 in 100) responds to the tests for
Sulfate 
191
.
Specific rotation 781S:
between
116
and
120
.
Test solution:
10 mg per mL, in water.
Loss on drying 731—
Dry it at 105
to constant weight: it loses not more than 1.0% of its weight.
Assay—
Dissolve about 200 mg of Physostigmine Sulfate, accurately weighed, in 25 mL of water. Render the solution alkaline by the addition of about 1 g of sodium bicarbonate, and extract with one 25-mL and five 10-mL portions of chloroform, each time shaking vigorously for 1 minute. Filter each extract through glass wool. Add 15 mL of glacial acetic acid and 10 mL of acetic acid anhydride to the combined chloroform extracts, and titrate with 0.02 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.02 N perchloric acid is equivalent to 6.488 mg of (C15H21N3O2)2·H2SO4.
