Abstract: A small D.C. motor (1) provided with a flat circular or square PTC thermistor (8) between an input terminal (7) and phosphor bronze plate (6) connected to the motor brush (5). The thermistor has electrodes on both faces and an opening provided substantially in its central portion, and it is fitted on the inside or outside of the motor casing (2). The motor shaft (9) or an extension thereof is passed through the opening in the thermistor in such a manner that the plate surface of the PTC thermistor (8) is nearly perpendicular to the shaft (9).

Abstract: A method for producing titanium fluoride comprises: a dissolution process, wherein iron-containing titanium material is dissolved in solutions containing hydrofluoric acid, fluoride solutions being produced; a first crystallization and separation process, wherein ferric fluoride is crystallized and ferric fluoride crystals thus obtained are separated from the fluoride solutions by cooling the fluoride solutions, crude titanium fluoride solutions being produced; a second crystallization and separation process, wherein a mixed salt of (NH.sub.4).sub.2 TiF.sub.6 and (NH).sub.3 FeF.sub.6 is crystallized and separated by mixing ammonium fluoride solutions with the crude titanium fluoride solutions to obtain a mixture and concentrating the mixture; a first pyrolysis process, wherein the ammonium fluoride salt is pyrolyzed at a temperature of from 300.degree. to 800.degree. C. in a stream of dry gas after having dried the ammonium fluoride, solid ferric fluoride (FeF.sub.3) and gaseous TF.sub.4, HF and NH.sub.