e dried
substance, add water until the contents of the flask weigh 110 grams,
connect with a reflux condenser and heat, beginning the boiling in 10 to
15 minutes. Boil for 1 hour, cool for 15 minutes, weigh again, making up
any loss by the addition of water, filter, and take the specific gravity
of the filtrate at 15 deg. C.

According to McGill, a 10-percent extract of pure coffee has a specific
gravity of 1.00986 at 15 deg. C., and under the same treatment chicory
gives an extract with a specific gravity of 1.02821. In mixtures of coffee
and chicory the approximate percentage of chicory may be calculated by the
following formula:

(1.02821 - sp. gr.)
Percent of chicory = 100 ------------------
0.01835

The index of refraction of the above solution may be taken with the
Zeiss immersion refractometer or with the Abbe refractometer.

With a 10-percent coffee extract, n_d 20 deg. = 1.3377.

With a 10-percent chicory extract, n_d 20 deg. = 1.3448.

Determinations of the solids, ash, sugar, nitrogen, etc., may be made in
the 10-percent extract, if desired.

24. _Caffetannic Acid--Krug's Method_[187]

Treat 2 grains of the coffee with 10 cc. of water and digest for 36
hours; add 25 cc. of 90-percent alcohol and digest 24 hours more,
filter, and wash with 90-percent alcohol. The filtrate contains tannin,
caffein, color, and fat. Heat the filtrate to the boiling point and add
a saturated solution of lead acetate. If this is carefully done, a
caffetannate of lead will be precipitated containing 49 percent of lead.
As soon as the precipitate has become flocculent, collect on a tared
filter, wash with 90-percent alcohol until free from lead, wash with
ether, dry and weigh. The precipitate multiplied by 0.51597 gives the
weight of the caffetannic acid.

[Illustration]

CHAPTER XVIII

PHARMACOLOGY OF THE COFFEE DRINK

_General physiological action--Effect on children--Effect on
longevity--Behavior in the alimentary regime--Place in
dietary--Action on bacteria--Use in medicine--Physiological action
of "caffetannic acid"--Of caffeol--Of caffein--Effect of caffein on
mental and motor efficiency--Conclusions_

By Charles W. Trigg

Industrial Fellow of the Mellon Institute of Industrial Research,
Pittsburgh, 1916-1920

The published information regarding the effects of coffee drinking on
the human system is so contradictory in i