compounds with "caffetannic acid," so that this reagent must be added
with extreme care in order to precipitate the compound desired. The
precipitate, upon forming, mechanically carries down with it any fats
which may be present, and which are removed from it only with
difficulty. The majority of the mineral salts in the solution will come
down simultaneously. All of the above-mentioned organic acids form
insoluble salts with lead acetate, and there will also be a tendency
toward precipitation of certain of the components of caramel, the acidic
polymerization products of acrolein, glycerol, etc., and of the proteins
and their decomposition products.

In view of this condition of uncertainty in composition, necessity for
great care in manipulation, and ever-present danger of contamination,
the significance of "caffetannic acid analysis" fades. It is highly
desirable that the nomenclature relevant to this analytical procedure be
changed to one, such as "lead number," which will be more truly
indicative of its significance.

_The Alkaloids of Coffee_

In addition to caffein, the main alkaloid of coffee, trigonellin--the
methylbetaine of nicotinic acid--sometimes known as caffearine, has been
isolated from coffee.[132] This alkaloid, having the formula
C_14_H_16_O_4_N_2, is also found in fenugreek, _Trigonella
foenum-graecum_, in various leguminous plants, and in the seeds of
strophanthus. When pure it forms colorless needles melting at 140 deg. C.,
and, as with all alkaloids, gives a weak basic reaction. It is very
soluble in water, slightly soluble in alcohol, and only very slightly
soluble in ether, chloroform or benzol, so that it does not contaminate
the caffein in the determination of the latter. Its effects on the body
have not been studied, but they are probably not very great, as
Polstorff obtained only 0.23 percent from the coffee which he examined.

Caffein, thein, trimethylxanthin, or C_5_H(CH_3)_3_N_4_O_2, in
addition to being in the coffee bean is also found in guarana leaves,
the kola nut, mate, or Paraguay tea, and, in small quantities, in cocoa.
It is also found in other parts of these plants besides those commonly
used for food purposes.

A neat test for detecting the presence of caffein is that of A.
Viehoever,[133] in which the caffein is sublimed directly from the plant
tissue in a special apparatus. The presence of caffein in the sublimate
is verified by observing its melting point, determined o