Abstract: Process for the recovery of hydrogen fluoride (HF) from a mixture, preferably an azeotropic mixture, of HF with water and/or an organic compound such as 134a, 125 or 133a, which comprises contacting the mixture with lithium fluoride or an alkaline earth metal fluoride to form a metal fluoride-hydrogen fluoride compound (e.g. lithium bifluoride, LiHF.sub.2), separating the compound and decomposing it to liberate hydrogen fluoride therefrom. The process is useful for recovering HF from azeotropic or azeotropic-like mixtures.

Abstract: A process for the removal of fluoride from a spent chromium-based fluroination catalyst by contacting the catalyst with potassium hydroxide to produce a suspension of solid hydrated chromium oxide in aqueous potassium fluoride. The solid hydrated chromium oxide may be separated from the solution, washed with water and/or aqueous acid, and contacted with nitric acid to produce a chromium (HI) nitrate solution from which a chromium-based catalyst may be prepared by precipitation of hydrated chromium oxide therefrom with aqueous alkali, and washing, drying and calcining the hydrated chromium oxide.

Abstract: Photosensitive polymeric compositions comprising a copolymer of (a) vinyl alcohol units and (b) vinyl ester units derived from the structure ##STR1## in which R is a divalent organic group, R.sup.1, R.sup.2 and R.sup.3 are organic substituents and X is an anion are disclosed. The ratio of (a) to (b) units is from 1:100 to 1000:1, units (a) and (b) together forming at least 80% of the copolymer. These copolymers are useful in forming films sensitive to ultra-violet radiation.

Abstract: Salts of N,N'-bis(p-cyanophenyl)-4,4'-bipyridylium are prepared by contacting an N,N'-bis(2,4-dinitrophenyl)-4,4'-bipyridylium salt with p-cyano-aniline in an inert polar medium.

Abstract: An electrochromic medium and electrochromic devices containing such mediums comprising an electrochromically active material, an auxiliary redox system comprising reversibly oxidizable metallic ions, for example iron, a complexing agent for the metallic ions, particularly a carboxylic acid such as tartaric acid, and an inert solvent.

Abstract: A device for the control of light transmission or reflection comprises one or more working electrodes, preferably arranged to form a display and having radiation transmission or reflection properties, an active material comprising an N(p-cyanophenyl) substituted derivative of a compound, usually bicyclic, having two conjugated nitrogen-containing rings in contact with the working electrode surface, a counter electrode, also in contact with the active material and ferrous ammonium sulphate as an auxiliary redox system.