EXPERIMENTAL
Preparation of Pigment Concentrate-Fresh beet-roots are grated;
the pulp is dried in a thin layer at 80” in a ventilated oven, and is
ground in a meat grinder to a coarse powder. This is treated, in
lots of 500 gm., three or four times successively with 1 liter of boiling
95 per cent alcohol, being filtered each time. Yellow pigments
and other troublesome contaminants are thereby removed. The
residue is dried and ground in a ball mill to a fine powder. 100 gm.
of the powder are suspended in 150 ml. of 95 per cent ethyl alcohol
and 15 ml. of a 20 per cent solution of hydrogen chloride in ethyl
alcohol (20 gm. in 100 ml.) are added. After the mixture has been
stirred for 20 minutes at room temperature, 350 ml. more of alcohol
are added and stirring is continued for 30 minutes. The solution,
which contains most of the red pigment, is then drawn off with
suction through a tube to the end of which a small Buchner funnel
covered with filter cloth is attached. A second extraction with
150 ml. of alcohol, 10 ml. of alcoholic hydrogen chloride, and, later,
300 ml. of alcohol is carried out in the same manner,and two more
extractions with, respectively, 150, 5, and 350 ml. of reagents.
The combined extracts are filtered and neutralized to moistened
Congo red paper with 9 per cent aqueous solution of lithium
hydroxide added dropwise with continuous mechanical stirring.
The precipitate is allowed to settle, and the supernatant alcohol
is siphoned off. The insoluble material is washed several times
by decantation with 95 per cent alcohol and is then suspended in
acetone and filtered. The product is dried at 60-70” in the ventilated
oven and is finally pulverized and preserved in closed containers.
The yield is ordinarily between 5 and 8 gm., depending
upon the variety of beets used.