Abstract: A clear air device to maintain the cleanliness of air in "clear rooms" and to ventilate said rooms has a casing with an air inlet grid and an air outlet grid, a preliminary filter, a ventilator and a high efficiency particulate air filter unit (HEPA). The preliminary filter, the ventilator and the high efficiency filter are arranged within the casing in such an order that the air drawn in through the inlet grid first passes said preliminary filter, then the ventilator and thereafter the HEPA. The wall of the casing is provided with one opening between the air inlet grid and the preliminary filter and one opening between the HEPA and the air outlet grid.

Abstract: A countercurrent washing column adapted to be used in purifying a crude crystalline material with a solvent. A suspension of the crystalline material is fed to the top of the column and flows downwardly therein countercurrent to a washing solvent. A vertically arranged agitator shaft is positioned in the column for axial rotation and carries a plurality of axially spaced paddles. Frusto-conical baffles and guide plates are arranged within the column to cooperate with the paddles to produce radially inward and outward movement of the suspension and solvent as they flow through the column.

Abstract: A device for tempering and/or sterilizing objects which must be kept free of contamination by foreign particles, such as for example, ampules sterilized in pharmaceutical preparations, has a housing and means for supporting the objects in the housing. A pair of gas distribution plates are mounted in the housing in spaced relationship to each other, on either side of the support means, and cooperate with means for supplying conditioned air to produce a laminar flow of the conditioned air downwardly over the objects being treated. The conditioned air has a substantially different temperature than the objects being treated and can be either heated or cooled depending upon whether the device is used for sterilizing or tempering. Because of the maintenance of laminar flow in the housing, the number of contaminating particles per space unit which can come into contact with the objects being treated is decreased.

Abstract: Crude DMT containing, as impurities mainly dimethyl isophthalate, dimethyl orthophthalate and p-toluic acid methyl ester, is purified with the use of solvents known to be useful for the recrystallization of DMT in such a manner that the crude DMT in molten state is introduced with agitation into the solvent, the temperature of which is maintained above the temperature of that eutectic mixture of DMT and the main impurities associated therewith which has the highest melting point. As soon as the solvent is saturated with DMT, pure DMT crystallizes. The process is preferably carried out continuously and in a special vertical counter-current washing column.