GB867811A - Apparatus sensitive to the water content of vapour above chemical cleaning liquids - Google Patents

Abstract

867,811. Humidity measurement. STOCKHAUSEN, J. Aug. 19, 1958, No. 26649/58. Class 40 (1). [Also in Groups XX, XXIII and XXXV] The water content of drycleaning fluid is measured by arranging a hygrometer in the vapour above the fluid in a chamber separate from the cleaning installation, the fluid entering and leaving by liquid seals. Preferably the hygrometer sensing member nearly fills the vapour space and the entering fluid runs down the walls of the space without coming into contact with the hygrometer, being kept away by a gaspermeable network or bars, e.g. the fluid can trickle over packing material in the chamber. The latter may comprise a double cylinder with the fluid between the walls. For accurate results the fluid should be brought to a constant temperature by passing it through a heatexchanger before it enters the chamber. The temperature may be 15-30‹ C. depending on the volatility of the solvent used. In Fig. I the fluid enters at 3 into a surrounding jacket and passes via 5 to form a constant head between the edges 7 and 11 before flowing down past the hygrometer element 9. The latter comprises a flat plate of insulating material containing a gold grid covered with a layer of lithium chloride whose conductivity varies with moisture content. The fluid then emerges via the liquid seal 6. The variation of resistance of the element produces electrical signals which can control the addition of water to the main body of fluid (see Group XXXV). The hygrometer can also be a non-electric type (see Group XX).