Abstract: The invention describes a method and a device for the continual and, in particular, for a fast detection of changes of the concentration of radon gas dissolved in water by means of a transfer into a measuring gas (Rn-222), which can be adopted for a variety of monitoring, control and regulation assignments. The invention is based on the fact that a membrane, which is permeable for the radioactive noble gas radon but extensively non-permeable for water, is circum-flushed on the one side of radon-containing water and on the other side of the carrier gas with, in each case, optimised flow velocities either in parallel or in counter-flow When stable peripheral conditions are ensured, the concentration of radon in the measuring gas is directly proportional to the concentration of radon in the water.

Abstract: The invention is a process for the hydrothermal production of crystalline sodium disilicate by heating an aqueous mixture of quartz sand and sodium hydroxide or an aqueous solution of sodium disilicate with a solids content of at least 50% by weight or more than 75% by weight at a temperature above 235.degree. C. and under autogenous pressure to form crystalline sodium disilicate.

Abstract: This invention is a process for the hydrothermal preparation of sodium disilicate with a molar ratio of Na.sub.2 O:SiO.sub.2 of 1:2 at an elevated temperature and a pressure corresponding to said temperature in a pressure vessel, characterized in that quartz sand and caustic soda solution and/or an aqueous solution of amorphous sodium disilicate at a total solids concentration of from 50 to 75% by weight are heated to at least 235.degree. C. in a first step, the concentration may be increased in an optional second step by removing water from the reaction mixture, in a third step, dependent on whether the second step has been carried out, the amount of water removed in the second step is completely or partially added again to the mixture during or immediately after same has been cooled to from 90.degree. C. to 130.degree. C., and then the obtained crystalline sodium disilicate is recovered.

Abstract: A process for working up water-soluble cellulose derivatives, more especially with flocculation points above 85.degree. C., after removal by condensation of readily volatile constituents of the crude product mixture resulting from an etherification reaction, by suspension of the crude product in hot water and subsequent separation of the suspension and washing liquids, wherein the separation of the suspension and washing liquids is carried out at elevated temperature and under pressure applied to the separator as a whole.

Abstract: Process and means for purifying cellulose ethers without flocculation points or with relatively high flocculation points (up to 95.degree. C.) and thermoplastic, i.e. highly propoxylated, products made from cellulose in any form, the crude product is first suspended and the suspension liquid subsequently separated in a reverse filter centrifuge a single-stage or multistage wash can be carried out. The filter cake is discharged by reversal of the filter cloth of the centrifuge.

Abstract: A process is disclosed for recovering a cellulose ether from a cellulose ether suspension in which the cellulose ether is recovered as a filter cake from a pressure filtration, particularly using a rotary pressure filter. Clogging of the separation or filtration device is avoided, providing for a long useful life. A multi-layer wire mesh filter medium is employed, formed of mesh layers of different wire thicknesses and/or mesh size. After removal of the filter cake, the filter medium is cleaned with steam, compressed air or pressurized water.

Abstract: A method for the preparation of finely-divided, water-insoluble, aluminosilicate cation-exchangers with a narrow particle size spectra suitable for detergent formulations comprising:(1) agitating a water-dissolved alkali metal silicate at a temperature of from 55.degree. C. to 95.degree. C.(2) mixing therewith at a temperature of from 55.degree. C. to 95.degree. C. over a period of from three seconds to five minutes with vigorous agitation, a water-dissolved alkali metal aluminate, in the presence of an excess of alkali to give a suspension of a silicate compound containing bound water and having a calcium binding power, when measured at 22.degree. C. by the Calcium Binding Power Test Method, of at least 50 mg CaO/gm of anhydrous active substance, and having the formula, bound water not shown,(M.sub.2 O).sub.0.8-1.3.Al.sub.2 O.sub.3.(SiO.sub.2).sub.1.75-2.0wherein M represents an alkali metal, wherein said reactant solutions when mixed have a composition corresponding to the desired Al.sub.2 O.sub.3 and SiO.