PHYSOSTIGMINE. 
419 
§ 501.] 
Rubreserine crystallises from water in deep-red needles containing 1 
molecule of water of crystallisation; m.p. when anhydrous, 152°. Crystal¬ 
lised from hot benzene, the crystals contain benzene of crystallisation 
and they melt at 100°. Rubreserine is neutral to litmus, but possesses 
both basic and acidic properties. It is insoluble in light petroleum or 
ether, but readily dissolves in water, alcohol, or chloroform, giving 
blood-red solutions. 
Rubreserine hydrochloride, C 13 H 16 0 2 N 2 C1, brick-red crystals, melting 
with decomposition at 185°. 
Rubreserine -pierate, bright red needles, m.p. 186°. 
Eserine blue is a dark blue powder readily soluble in alcohol, chloro¬ 
form, or water, the solutions being intensely blue. It is a strong base, 
forming salts with two equivalents of an acid. The hydrochloride, 
C 17 H 23 0 2 N 3 2HC1, crystallises in blue needles, which by reflected light 
have a bronze-like lustre. The needles are soluble in water, giving a 
deep blue solution ; on the addition of a little acid a beautiful carmine- 
red fluorescence is produced. The aurichloride, minute violet prisms, 
begins to decompose at 165°, and contains 40 per cent. gold. 
Physostigmine sulphate (eserine sulphate), minute white crystals, 
becoming yellowish on exposure to air and light; very deliquescent. 
Readily soluble in water, soluble in alcohol (90 per cent.). Aqueous 
solution neutral to litmus ; yields the reaction characteristic of sulphates ; 
yields with dilute solution of sodium hydroxide a white precipitate 
turning pink and forming a red solution with excess of the reagent. When 
mixed with solution of ammonia and evaporated to dryness on a water- 
bath it leaves a bluish residue, the solution of which in very dilute acids 
is dichroic, being red by reflected and blue by transmitted light. A 
minute fragment dissolved in a few drops of fuming nitric acid forms a 
yellow' liquid, which, on warming on a water-bath, turns orange, then 
blood-red, and on evaporation to dryness leaves a green residue ; this 
residue turns violet-blue on exposure to the fumes of nitric acid, and 
when moistened with the acid gives gradually a blood-red colour, 
which changes to yellow-green on the addition of water. A dilute 
aqueous solution applied to the eye causes contraction of the pupil. 
No appreciable ash. 
Physostigmine ( eserine ) discs for ophthalmic use are official; each 
disc contains 0-065 mgrm. of physostigmine sulphate. 
§ 501. Tests. —Da Silva’s 1 test for eserine is as follows :—A minute 
fragment of eserine or one of its salts is dissolved in a few drops of 
fuming nitric acid ; this makes a yellow solution, but evaporated to 
complete dryness it is pure green. The green substance, called by others 
chloreserine, dissolves to a non-fluorescent green solution ; in water and 
also in strong alcohol it shows a band in the red between A 670 and A 680, 
1 S. J. Ferreira da Silva, Compt. Rend., cxvii. 330, 331. 
