show merely the relative position occupied by caffein in
the purin group, and do not in any wise indicate, because of its
similarity of structure to the other compounds, that it has the same
physiological action. The presence and position of the methyl groups
(CH_3) in caffein is probably the controlling factor which makes its
action differ from the behavior of other members of the series. The
structure of these compounds was established, and their syntheses
accomplished, in the course of various classic researches by Emil
Fischer.[137]

[Illustration: FORMULA FOR CAFFEIN, SHOWING ITS RELATION TO THE PURIN
GROUP]

Gorter states that caffein exists in coffee in combination with
chlorogenic acid as a potassium chlorogenate, C_32_H_36_O_19,
K_2(C_8_H_10_O_2_N_4)_2.2H_2_O, which he isolated in colorless
prisms. This compound is water-soluble, but caffein can not be extracted
from the crystals with anhydrous solvents. To this behavior can probably
be attributed the difficulty experienced in extracting caffein from
coffee with dry organic solvents. However, the fact that a small
percentage can be extracted from the green bean in this manner indicates
that some of the caffein content exists therein in a free state. This
acid compound of caffein will be largely decomposed during the process
of torrefaction, so that in roasted coffee a larger percentage will be
present in the free state. Microscopical examination of the roasted bean
lends verisimilitude to this contention.

[Illustration: PLANTER'S BUNGALOW WITH COFFEE TREES IN FLOWER, MYSORE]

[Illustration: COOLIES BAGGING COFFEE ON THE DRYING GROUNDS]

[Illustration: COFFEE SCENES IN BRITISH INDIA]

TABLE II--COFFEE ANALYSES

Santos Green
| Santos Roasted
| | Padang Green
| | | Padang Roasted
| | | | Guatemala Green
| | | | | Guatemala Roasted
| | | | | | Mocha Green
| | | | | | | Mocha
| | | | | | | Roasted
| | | | | | | |
Moisture 8.75 3.75 8.78 2.72 9.59 3.40 9.06 3.36
April 20th
Moisture
September 20th 8.12 6.45 8.05 6.03 8.68 6.92 8.15 7.10
Ash 4.4