r liquids. The tubes are
easily reached through the open door for cleansing. Interior of the
vapor body is reached through a manhole.

REAR VIEW OF DRUM DRIER

Vacuum drum dryer. No. 1 size; rear view, showing outer casing rolled
back from the drum.

CROSS-SECTION OF VACUUM DRIER

This shows the interior arrangement and principle of operation. The
drawing represents a larger size than the photograph, and while the
arrangement of some parts is slightly different, the principle of
operation is the same.

UNITS USED IN THE MANUFACTURE OF SOLUBLE COFFEE]

In manufacturing dry coffee extract in the form of a powder that is
readily soluble in water, the general method is to extract the drinking
properties from ground roasted coffee by means of water, and to
evaporate the resulting liquid until only the coffee powder is left.
Several methods have been developed and patented to prevent the valuable
flavor elements from being evaporated with the water.

A typical dry-coffee-extract-making equipment consists of a battery of
percolators, or "leachers", a vacuum evaporating device, and a vacuum
drier. The leachers do not differ materially from the ordinary
restaurant percolators, a battery usually including from three to seven
units, each charge of water going through all the percolations. The
resulting heavy liquid then goes to the evaporator to be concentrated
into a thick liquor. The evaporator consists of a horizontal cylindrical
vapor compartment connected with an inclined cylindrical steam chest in
which are numerous tubes, or flues, that occupy almost the whole chest.
These tubes are heated by steam. The coffee liquor is passed through the
tubes at high speed and thrown with great force against a baffle plate
at the opening to the vapor chest. The vapor passes around the baffle
plate to a separator. The liquor drops to the lower part of the
steam-chest (which is free from tubes), and is ready to be drawn out for
the next process, the drying.

At this stage, the extract is a heavily concentrated syrup and is ready
to be converted into powder. This is done in the vacuum drier, which
consists of a hollow revolving drum surrounded by a tightly sealed
cast-iron casing. The drum is heated by steam injected into its
interior, and is revolved in a high vacuum. In operation, a coating of
coffee liquor is applied automatically, by means of a special device, to
the outside of the drum. The liquor is taken by gravity from the