for which purpose we dissolve it in a little lukewarm alcohol, then
quickly cool the solution; flakes of a fatty substance will be
separated, which are removed by filtration with the aid of a
suction-pump. Then we throw a few small crystals of the acid into the
solution, and after a short time crystallization commences. As soon as
it appears to be ended, the mother solution is removed with the aid of a
platinum cone, and the crystals washed with a little cold alcohol. The
alcoholic mother solution, which still contains the chief part of the
bitter acid, must be quickly evaporated, and the residue consigned to
a flask. The acid crystallized from the alcohol is then recrystallized
several times from petroleum-ether. In order to quickly dissolve the
bitter substance, it should be carefully melted in a flask, and double
its volume of ether gradually added; on its cooling, we obtain beautiful
prismatic crystals, which attain a length of 1 cm., and become perfectly
pure after four or five crystallizations. The mother solutions must be
speedily evaporated if we still wish to obtain crystals; after a time
they will only furnish a resinous residue.

The hop-bitter acid melts at 92 deg. to 93 deg.. It is easily soluble in
alcohol, ether, benzol, chloroform, sulphide of carbon, and vinegar; to
a lesser extent in cold petroleum ether, and not at all in water.

In the analysis I obtained figures which correspond best with those
calculated from the formula C_{25}H_{35}O_{4}.

Obtained.
Calculated. ------------------------^-----------------------
-----^----- 2. Crystal. 3. Crystal. 5. Crystal. 6. Crystal.
p.c. p.c. p.c. p.c. p.c. p.c. p.c.
C 75.19 74.79 74.83 74.9 75.04 75.05 75.07