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LIL— ON A SEPARATING APPARATUS FOR USE WITH 

 HEAVY FLUIDS. By PROFESSOR SOLLAS, LL.D. 

 (Plate XIII. , Fig. 1.) 



[Read, January 19, 1887.] 



Amongst the difficulties presented by the method of separating the 

 mineral constituents of rocks with the aid of heavy fluids are two 

 which the apparatus to be described fully overcomes. These are : 

 first, that of removing the separated mineral from the apparatus ; 

 and next, that of effecting a rapid mixture of the fluid already in 

 the tubes, and that which is added to reduce its density. The first 

 is readily met, by using two tubes, which are united by a joint, with 

 ground surfaces (fig. 1, a) ; the second, by closing the tubes with a 

 stopcock at each end (s, s'), so that after each addition of dilute fluid 

 the apparatus may be inverted. In using this apparatus, the heavy 

 fluid having been introduced, the powdered mineral is added and 

 allowed to separate. When the separation is complete, the stop- 

 cocks are all closed, and the two tubes separated from each other. 

 If any mineral remains above the stopcock ($'") it may be washed 

 into the upper tube ; the lower tube is then supported over a funnel 

 containing a filter paper, and the contents allowed to run out by 

 opening both stopcocks (/, s'"). If any particles of the mineral 

 remain behind adherent to the sides of the tube, they may be 

 washed out by water. The tubes are then fitted together again, 

 the stopcocks opened, and diluted fluid or water added; the ter- 

 minal stopcocks at each end are then closed, and the tubes turned 

 one and the other way up till perfect admixture is obtained ; the 

 whole is then left to settle till another separation is accomplished. 

 To furnish the experimenter with approximate information as to 

 the specific gravity of the liquid in the tubes, and to enable him to 

 obtain approximately a desired specific gravity, the tubes are gra- 

 duated so that the specific gravity of the fluid used at starting being 

 known, and its volume also a measured volume of the diluent of 

 known specific gravity can be added. 



It may be useful if I here add a short account of the course of 

 mechanical separation and associated operations, as carried out in 



