Oils and Fats. 



126 



tions on the .shaft form a prolongation of the tube. It is evident that the paddles 

 ought to turn in opposite directions, so as to produce a uniform and energetic 

 agitation of the oil. When the paddles are turning, the oil is subjected to a strong 

 agitation and froths very freely, the froth having of course the tendency to escape by 

 the air tube ; to avoid this, while giving to the gases formed the possibility of 

 escaping freely, a ventilator of special form is connected with the apparatus. 

 This consists of a box which communicates with the air tube and which is furnished 

 with a shaft. This receives its movement by means of the toothed wheel and 

 another toothed wheel mounted on the principal motive shaft. The shaft is 

 furnished radially with several wings, at the extremities of which are fixed 

 the small movable paddles. By means of this arrangement the air and gases 

 formed, which penetrate into the air tube, may escape freely to the open air, while 

 the froth is broken up in the box and forced back to the inside of the 

 kettle. Below the socket of the shaft a sieve is arranged, a metallic cap, which 

 in its upper part has notches around it ; these serve for obtaining a better distri- 

 bution of the air passing through the oil. The extremity of the worm air tube 

 penetrates this cap, the air is forced back into the kettle under a pressure always 

 constant, by means of an air pump or other suitable arrangement. The air tube 

 may be surrounded with a metallic jacket ; the admission of air into the worm 

 and under the cap is regulated by means of the tap, which is furnished with a scale 

 and an indicator, and may, if needed, be arrested completely. 



The working of the apparatus takes place as follows:— The kettle is 

 about two-thirds filled with linseed or other vegetable oil to be treated, steam is 

 admitted into the chamber and the oil is heated to at least 100 deg. C. The 

 paddles are then submitted to an active movement in such a way that the contents 

 of the kettle are stirred very energetically. The agitation is continued for about 

 three hours, that is, until the wished-for degree of decolouration is secured. 

 During this period the tap may remain closed and the compressing ^irrangement be 

 stopped. When the decolouration has been secured its concentration commences, 

 keeping the agitator in movement but applying the compression and gradually 

 opening the air tap. The air heated by the worm enters the cap and is forced 

 back into the oil in the form of bubbles or small jets, so as to facilitate the 

 vapourization and escape of the particles of air contained in the oil. The 

 complete elimination of all these particles of water is secured by the high 

 temperature, at least 100 deg. C, and by the action of the paddles, which divide the 

 air admitted with the oil very finely. The air and the vapour formed escape 

 by the air tube while the froth is always brought back into the interior of the 

 kettle by the action of the ventilator. This operation continues for about 11 

 hours, according to the degree of concentration desired, after which the pre- 

 pared oil is drawn off by a tube into corresponding receivers. After an operation 

 of about 11 hours there is in the kettle a tenacious elastic matter (oil caoutchouc), 

 which cannot be drawn off by the exit tube ; for removing it, it is necessary to 

 open the apparatus and remove the agitator, when the matter can be taken from 

 the paddles and walls of the apparatus ; it may be easily raked off. The oil which 

 has been submitted to this operation is completely decoloured and exhibits great 

 lustre and elasticity, which it preserves indefinitely ; at the same time it has 

 the property of absorbing large quantities of liquid with which it may be diluted. 

 This method is much less expensive than the ordinary process and also econo- 

 mizes the time. In a few hours, instead of several days and even weeks, the 

 operation is terminated. For accelerating the drying of the concentrated oil, 

 the compression tube can be passed, if desired, though a retort filled with 

 manganese oxide or other substance restoring oxygen readily, so that the oxygen is 

 forced back by the tube into the kettle, and the oil is dried rapidly. For causing 

 the longer sojourn of the air and for distributing it more regularly in the 

 mass of oil. perforated horizontal disks can be arranged on the mixer.— La Revue 

 de Chimie Industrielle. 



