all of the vitamine originally present in the yeast but attempts to
precipitate the vitamine fractionally from the evaporated filtrate by
means of increasing concentration of added alcohol has been only partially
successful. The method however yields a concentrated extract, and Harris
has made use of this process to prepare tablets for medicinal purposes.

Seidell and Williams some time ago devised a procedure which seemed to
give promise of good results. Their discovery was that when a filtrate
from autolysed yeast is prepared, rich in the vitamine, and is shaken with
a specially activated fuller's earth (the preparation produced by Lloyd
and known as Lloyd's reagent has this power) in a proportion of 50 grams
to the liter of extract the vitamine is absorbed by the earth and when the
latter is filtered off it carries the vitamine with it. In their process
they shake the mixture for about one-half hour and then remove the earth
by filtration. Analysis of the yeast liquor after the extraction shows it
to contain practically the same solids as originally present but to have
lost practically all its vitamine. The latter is firmly attached to the
earth and repeated washing with water fails to remove any appreciable
amount of vitamine from it. Furthermore the vitamine-activated fuller's
earth retains its active vitamine properties for at least a period of two
years. Large amounts of the vitamine can be accumulated in this way and
when fed to animals or infants the vitamine is liberated physiologically
and produces the usual effects of a vitamine extract. When this discovery
was made the discoverers thought that in the fuller's earth they had a
means for arriving at the identification of the substance but attempts to
recover the vitamine from the earth developed unexpected difficulties.
Acids were found to split it off but they also split off aluminium
compounds and left an impure mixture little better than the original
extract for study. By using a dilute alkali they were able to obtain the
substance without aluminium contaminations and by this method they