cose, sucrose, lactose, or dextrin to green coffees
is practised by von Niessen[117] and by Winter[118], with the object of
giving a mild taste and strong aroma to "hard" coffees. The addition is
accomplished by impregnating, with or without the aid of vacuum, the
beans with a moderately concentrated solution of the sugar, the liquid
being of insufficient quantity to effect extraction. When the solution
has completely disseminated through the kernels, they are removed and
dried. Upon subsequent roasting, a decided amelioration of flavor is
secured.

Another method developed by von Niessen[119] comprises the softening of
the outer layers of the beans by steam, cold or warm water, or brine,
and then surrounding them with an absorbent paste or powder, such as
china clay, to which a neutralizing agent such as magnesium oxid may be
added. After drying, the clay can be removed by brushing or by causing
the beans to travel between oppositely reciprocated wet cloths. In the
development of this process, von Niessen evidently argued that the
so-called "caffetannic acid" is the "harmful" substance in coffee, and
that it is concentrated in the outer layers of the coffee beans. If
these be his precepts, the question of their correctness and of the
efficiency of his process becomes a moot one.

A procedure which aims at cleaning and refining raw coffee, and which
has been the subject of much polemical discussion, is that of Thum[120].
It entails the placing of the green beans in a perforated drum; just
covering them with water, or a solution of sodium chloride or sodium
carbonate, at 65 deg. to 70 deg. C.; and subjecting them to a vigorous
brushing for from 1 to 5 minutes, according to the grade of coffee being
treated. The value of this method is somewhat doubtful, as it would not
seem to accomplish any more than simple washing. In fact, if anything,
the process is undesirable; as some of the extractive matters present in
the coffee, and particularly caffein, will be lost. Both Freund[121] and
Harnack[122] hold briefs for the product produced by this method, and
the latter endeavors analytically to prove its merits; but as his
experimental data are questionable, his conclusions do not carry much
weight.

_The Acids of Coffee_

The study of the acids of coffee has been productive of much controversy
and many contradictory results, few of which possess any value. The acid
of coffee is generally spoken of as "caffetannic acid." Q