Abstract: A continuous process is disclosed for the production, with a high yield, of high purity silicon tetrafluoride, starting from an aqueous solution of fluorosilicic acid, which comprises:(a) reacting an aqueous solution of fluorosilicic acid with concentrated sulphuric acid, carried out with a short residence time and preferably under fluido-dynamic conditions of turbulence, inside a reaction zone;(b) separating a gaseous stream containing silicon tetrafluoride from a liquid stream of aqueous sulphuric acid, carried out inside a separation zone, directly connected with the reaction zone;(c) washing said gaseous stream with concentrated and cold sulphuric acid carried out inside a washing zone, for the purpose of separating a gaseous stream of purified silicon tetrafluoride; and, possibly(d) further purifying said gaseous stream of purified silicon tetrafluoride by means of techniques of adsorption on an adsorbent solid material.

Abstract: A process is disclosed for the preparation of potassium nitrate by means of the reaction of nitric acid with potassium carbonate, wherein potassium carbonate is obtained by means of an electrochemical process.

Abstract: In a chain-driven comb head for drawing frames, of the type including means for directing compressed air jets at the combs, these means comprise ducts for supplying compressed air to each needle field defined by the combs and slots for generating, from the supplied air, at least one flat jet of compressed air directed outwardly in a predetermined direction which does not intersect the zone of treatment of the sliver between the combs. During movement of the combs, the flat jet of compressed air flows successively over the surfaces of the combs to clean them. The needle-carrying bars making up the combs are rotatably mounted about their axes and have one end out of alignment, the head structure including at least two tracks engaged by the non-aligned ends and shaped so as to cause the combs to orient themselves in a predetermined direction when they pass in front of the flat jet.