THE ATTEMPTS TO DETERMINE THE CHEMICAL NATURE OF A VITAMINE

The discovery of the existence of an unknown substance is naturally a
stimulation to investigation of its nature. In the case of the vitamines
we have many researches to this end but extremely meagre results. We are
today actually no nearer the goal of identification than we were in 1911
when Funk published his studies on the beri-beri curing type. In brief, we
do not know what a vitamine is. Nevertheless, it will be of interest to
the student to review the attempts that have been made to isolate these
substances for such attempts must furnish the starting point for further
studies and their description will help to make clear the nature of the
problem involved.

The most extensive investigations have dealt with the first type
discovered, namely the vitamine "B" or Funk antineuritic type. In 1911
Cooper and Funk found that the alcoholic extract of rice polishings could
be precipitated with phosphotungstic acid and that this procedure
permitted them to obtain a fraction that was particularly potent and free
from proteins, carbohydrates, and phosphorus. Funk carried this
investigation farther and fractioned the phosphotungstic acid precipitate
with silver nitrate, following the usual procedure for separating
nitrogenous bases. From the silver-nitrate baryta fraction he obtained a
crystalline complex melting at 233 C. to which he gave the formula
C_17H_20O_7N_2. This substance was curative for pigeons and the
fractioning process was applied by him to yeast and other foodstuffs with
similar results. From these results Funk believed the vitamine to belong
to a class of substances known as the pyrimidine bases. Later, when
working with Drummond, Funk was forced to admit that his crystalline
complex was not the pure substance, as analysis showed that it contained
large amounts of nicotinic acid. His product might well be considered as