218 



KNOWLEDGE. 



Junk, 1911. 



funiifl sliould be covered by a piece of clean paper. 

 The heavy mineral ,t;rains should now collect in the 

 portion between the clip and the neck of the funnel. 

 When no further movement can be detected the 

 stopper is plunged beIo\\ the surface of the li(iuid. 

 and moved carefully to and fro several times, to rid 

 it of any grains which ha\e been carried down on 

 its low er extremity, and then inserted in the neck of 

 the funnel with a rotary motion which fixes 

 it firmly in the neck. The plug X is 

 removed and the thistle funnel liead "\' 

 inserted in its place. A second fniiiiel 

 with a folded filter pajier in it is placctl m 

 the neck of the solution bottle which i> 

 placed beneath the apparatus. 



The clip is next opened (juickly. and 

 the li([uid from the portion below the 

 stopper flows out carrying with it the 

 heavy grains. More fresh li(]uiil is now 

 poured into the thistle funnel which fiows 

 down anil washes an\- adhering grains 

 out. The clip is then closed again. 

 The filtered liquid fiows back into the bottle 

 and can be used again, while the grainj 

 are retained on the filter i)aper (funnel A) 

 Figure 4. 



The stopper is now removed, and put ,■ 



aside to be w^ashed. A third funnel with 

 filter paper is also placed in the neck of the bottle 

 which is again (placed below the apparatus. The 

 clip is opened again and all the li(|uid fiows out 

 carrying with it the b^i^btcr portion of the grains. 

 .\n additional arnimiit n| Hcpiid iioincd 

 in the separating tunnel will also How 

 out and carry witli it an\- remaining 

 grains which have adhered to the funnel 

 or tubes. The liquid will filter into the 

 bottle, while the grains will be retain(_'( 

 on this second paper (funnel B). All 

 that now remains to be done, i)reparator\- 

 to mounting for examination, is to wash 

 the grains thoroughl}-. The liquids used 

 being fairly expensive, it is also desirable 

 to perform this washing economicalh'. 

 The tollowing suggestions are offered 

 with a \-iew to collecting the washings 

 from the various funnels, papers, and Figure 5. 



grains, for ct)ncentration. If all the 

 are so retained in a stock bottle and 

 call}- treated suitablw great saving is 

 since the resulting concentrated solution ma\' be 

 used for fresh separations. 



There will thus be three funnels to be washed : — 

 (1) the separating funnel : (2) funnel A with the 

 heavy grains; (J) fuimel 15 with the lighter grains. 



It is suggested that a retort stand with three 

 narrow rings, or any stand with three sui)ports 

 capabk' of holding the three funnels in such a 

 positinii that they are \eiticall\- over each other, be 

 used, b'igure 4 gives a diagrammatical represen- 

 tation of the arrangement. 



In the top ring is the separating funnel, with 

 the sjiring clip removed and the stopper resting in it. 



In the middle rint 



tunnel B 



rh has the filter 

 paper holding the lighter grains. The lowest ring 

 supports funnel .\ which has the heav\- grains on 

 the filter paper. It is advocated that these funnels 

 be arianged in this order for the following reason. 

 .\ny grains, which will belong to the lighter portion 

 of the separation, which ha\e not been 

 washed down ivnm the separating funnel, 

 NN ill tall down to funnel 1! \\ith the 

 washing \\;ilcr, and so join tlii' pro- 

 per set ol ,i;rains. It fininel A were 

 [)laced in the middle there would be 

 a danger of these grains getting into 

 the wrong set. 



-V fine spray ot distilh.d water is directed 

 nil to the surface of the top funnel from 

 a wash bottle, and this water, after 

 cleaning that funnel, passes down through 

 r> and .\. finally enterini; the stock 

 buttle of washings placed underneath. 

 I'ue or six such washings should suffice 

 to clean the grains and a[)paratus. 



The filter [japers bearing the grains 

 ma\' next be dried in a steam oven, or 

 '"' in any dry place free from dust. 



The chief defect in this apparatus, which is 

 common to all similar ones, is that the separation is 

 not entirel\' reliable, owing to surface tension and 

 similar small attractions which are ine\itabl\' present 

 in the liipiid. h'igure 5 shows the 

 chief regions where these operate. In 

 the shaded portions the grains are 

 under slight attractions, due to the 

 above-mentioned causes: consequently 

 heavy grains which get into these mar- 

 ginal parts, ma\' iKit sink properly. 



At X and \' particularlw there is a 

 tendenc}' tor the grains to climb up 

 the sides of the funnel, al)o\e the 

 mean le\el of the lii]uid, where the 



ass 



lopmj: 



,da 



w aslnngs 

 periodi- 

 effected, 



meniscus touches the 

 sides. Great care and perse\erance 

 are necessary to overcome this and 

 other ine\'itable difficulties. 



ISy keeping three sets ot this apparatus in use on 

 one stand tor liijuids of different densities, the grains 

 may be sorted into four sets. 



Using litjuids of Specific Gravit}-, 2-7, 2-9, and 

 3-1, the following sets ma\- be obtained : — 



(1) Specific Gra\it\' less than _'•/. 



(2) Specific Gnwity between 2-7 and 2-'). 

 (.5) Specific Gravity between 2-'' and .)•!. 

 (4) Specific Gravitv greater than .>• 1. 



B\' increasing the 

 grains ma\- further be 

 restricted sets. 



nuinlier ot 

 clitferentiatinl 



quids, the 

 into more 



