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Optimum conditions for the flotationa of sphalerite by iso amyl xanthate Harrison, T. Allan 1942-11-15

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OPT IHUM C OICOIEIOITS FOE SHE FLCffiAMGI 01? SPHALBBIf Til Bf . IS© A i l L submitted for olio decree of : MAS513H OF ARES' - • ' - w • • Department of •GhmrlstTj University of B r i t i s h ColraiMa 1948 I t i s . a t q t j great pleasure to aclmowledge the help and guidance of Br* W» Tfre®, xmH&T wkos© diasetioit, t h i s worli was eaa?3?ie& out* • Introduction l^QzlmCTtt^L. work - jlateriels Apparatus Flotation tests w i t t e t collector ELot&tion testa varjiag c o l l e c t o r f l o t a t i o n tests T&sfyitig pH Dec opposition of scant Iiate Effect of decomposition on c o l l e c t i o n Abstraction Discussion of abstraction results References . In esperiiaontal investigo.-!;ion of the f l o t a t i o n ox minerals* two teehniqtiQS are i n general use: the "contact angle" method as developed "by i?ark end Cox, and tiie* direct f l o t a t i o n mo tho a, i n which an expsr- iraontal c o l l i s rtscd, operating on the same principle &s those uoocl coiamereiallyc doing ths second method, the Dehaviotrc of -fotas- sinra othyl jtanthats as a col l e c t o r of sphalerite has "boon investigated i n t h i s 1 ah oratory for tho paot several '/oars. I t was desired,, hor/ever, to compile gos'-'O data as to the hohsviour of soma other collectors v/ith tho osse ore and under the sane conditions., i7ith this i n trim the present tvoid-i was iiridertalcen, using potassium iso-arayi stanthate as osseiople® general opinion seems to be that pure aphal- orlto v / i l l not f l o a t unless activated, Oaudind) how ever, states that with collectors containing an alky! Group of f i v s carbon3 or more, f l o t a t i o n i s posoihle v/lthcml; activation and submits data indicating that uit J i ranthates containing the ethyl, n-aciyl and n- hoptyl groups,, col loot ion of sphalerite increases i n that order. He also finds a groat variation of recovery of nnaetivated sphalerite at constant pli (S.S) v.nlnr; potaeolna n-exn^l saathat© at ooiiesiitratioBs ranging from soro to .6 Ib./ton r;ith a Bayissinvi of Ghent 46,J at ths l a t t e r . C«H«M» del Girl dice (2) quo-ces a»a sodorses §a«din.* Hoyass and Haas, to^he effect that using arayl xsatfcat©the aaslinaa recovery of ui i a c t i - vated sphalerite eomos i n the pE range from 3.4- to 5«4, but does not state what recovery v/as obtained» Swains©n and ^ndorson (3) however, express the b e l i e f that com paring various Kanthates as collectors, t h e i r a c t i v i t y reaches a Haxinran at four carbon atoms and that for any number of carbons, the secondary compound i s best, • followed by i s o - and noivial. Chair data era based on copper and lead ores however, not OH sphalerites i'/arls and Cox (4) express the view* based on t h e i r aeasursments of contact angles, that i n concen trations of S5Eg»/l«B iao-arayl scant hat© w i l l not f l o a t (inactivated sphalerite* In a l a t e r a r t i c l e (5) they state that i n higher concentrations (up to. 300 nig./ 1- J e or i n acid solution, ( c r i t i c a l pH 5.5), eon* tact i s possible*-, With regard to possible decomposition of the orayl xamtliste i n use, available fiata#6)„(?) indicato extensive decomposition of ethyl xanthate In eeicl solution* Similar behaviour on the part of the arayl Kanthate eould b© expected and was investigated i n the OO- jv 'GO of the motIc* Materials rp&Q different samples of o%& were used-*. A« Source: Pari: i n color sad when ground fine retained t h i s color- ffho esact composition was not determined, hut rough analysis indicated appr o:ci Kate 1 y 1 'I of copper i n the ore* 2Ms would, indicate that the ore was prohably activated,, at least p a r t i a l l y • 15* Source: Ottawa County, Olda* Dark colored when i n largo pieces 9 hut r/hen hroken up had a resinous ap pearance and when "ground fine was creamy white i n color. * J!o copper could he detected. Potassium 4so~sia;yl saethate was zaade hy the usual method iron C i-aioj/1 alcohol, carbon a i - oulphide and potassium hyftrozido. I t was diosolved i n Bcetoa®, c r y s t a l l i s e d twice from bensea©, dried and stored over sulphuric acid i n a desiccator* i'erplneol was used as frothor i n e l l toe to, a stock solution of 250 Mg./l, "being made up and amounts froia 10 to 25 u l . as reouiracl .v*ers placed i n tho c e l l along with the oro. Hie amount recjuired varied considerably with the pE at which the test was made, strongly haoic solutions requiring more t©j'pineoi.0 Apgarattig The ore was ground i n a laboratory P&WI& r a i l l with porcelain 2b,t ana, f l i n t pebbles* I t was sized i n an. e l u t r i a t o r as- described by Her&O).* the ore.having a s e t t l i n g rate between 8 and 16 cm* per aiirote being use a for a l l tests*- 2Ha s e l l used for f l o t a t i o n tests was a modification of the design by Sennet' a pyres f r i t t e d glass f i l t e r being sealed to'a piece of pyres tubing of the same diameter as the f i l t e r and SI os® long- A l i p v&& formed at the top of the tube to provide for an overflow* 9Jwo pli meters were used j an i n d u s t r i a l model Beoiinan with glass and ealorael electrodes f o r mD&surement of pH; and a research model Beclcnan with platinum and calomel electrodes i o r t i t r a t i o n s , f l o t a t i o n Tests I without Collector Gaudin (10} and Taggart, del Oividlee and iSionl 111), state that sphalerite has no native f l o a t - a b i l i t y , that i s * i t v^ .11 not fl o a t i n the presence of frother alone. In order to test the char a c t e r i s t i c s , of the c e l l and also the ore 6 both# ore samples \7©re tested by the following method* To a weighed* dry sample of the ore i n a beaker, about 200 ml. of water and 5 ml* of 81? ammonium acetate were added*' pii w»ts adjusted on the meter by additions of HOI or KOH as required* rfha water used i n .oil tects and o i l solutions throughout th i s Y/orlr was d i s t i l l e d , the only exception being e l u t r i a t i o n of the ore. flie 5 ammonium acetate iiras foti^fl necaosary sine© xrithout i t pH dr i f t e d considerably during the test-,, and p r e l i a i n - as^r tests indicated that i t had no. appreciable effect' on the f l o t a o i l i t y of the ore* Shis aistttgs was then placed i n the c e l l 9 10-8S ml« terpineol. were added ae needed and the volume t/as made up to 800 ml. A i r was turned on and adjusted to a pressure of 34 OBI, of mer cury, which pressure .seemed to work "beat wit& t h i s c e l l , • 5?he overflow was caught i n a bealcer and wben the froth had become clean, the overflow was f i l t e r e d tlirongli a weighed gooeh. crucible. She weight of heads was com pared the the sample weight to give a measure of the recovery obtained, expressed as per cent* . j^.arge maa- hsr of tests were made over a large pii range with ore A, the rc3P.lt3 of some of which are given i n Sable I* yhere i s no regular variation with pH noticeable« Also„ some factor not under control hae a large effect on the recovery at any one ol-U A simi l a r set of tests on Ore 3 gave an indication of regularity with pH, tliongii not enough tests were Hade to walre such a conclusion d e f i n i t e , Hesnlts of thSL set of tests are given i n Table 11 and Fig* 1*. ' 2A3LI3 1 Bscovery without co l l e c t o r - Osfa.fut pH sample weight •% recoverjr '•2,2 5.001 eg 1.16 2*7 5.000 4,00 3.6 6.001 5,30 4.5 S.004 §.84 4*5 • 5*001 8»1 -.5.5 1*000 »8 7*5 5*001 *74 9*0 S.000 - .06 5.0*9 5*000 1.2 Recovery without co l l e c t o r - Ors B pH . sample weight $ recovery 2.0' - g.00 18..4 4*0 &» .. 5*0 a&- S2#4 .6*0 -fie • 44*6 6*0 .. . to 0.5.*9 8*0 ' -do 18*5 10*0 _ dO' 17*2 '13*0 do 12*6 7 I I ' O o f f l J l ^ ^ ^ L ^ t & l ^ l a S , aaou-nts of cojj.ecto^r SMs .series of -teste was eondactefl only with Ors A* Procedure- was as outlined above, except, that just "before a i r was "blown into -the c e l l , a measured amount of a standardised.solution of the xanthate was added» i a -Tolumes corresponding to the amounts of c o l l e c t o r shows i s the table* fh©.volum© was 300 ft s i . * ' i s a l l oases*.- Basalts*' are shown fo r two complete series at p i 4 and 8*5 in'table I I I sad Irig* 2* .Also shoxfii are a few results obtained at ,pH..2*0 and 2*8 , 'though these series ar© not complete* As soon as a f r o t h head formed, when collection was good* th© froth became very heavily mineral!sed* Shis formed a heavy cafe© on top of the c e l l which had. .to he scraped off* f his behaviour was expected since i t had been B O B - t i o n s t as a characteristic of amyl xsiithat.e hy Saudis •{12} and Balston and Barfesr-flS}* . f Wzm$ tho curves-of f i g * 2.* i t i s -seen-, tnat l a f a i r l y acid .solution* the colleeto-r i s effective i n very small fU-autitiss,. shout 1 Big.* being a l l . that i s required to produce raaxiiaurg recovery*. In tho basic range however* .more colle c t o r i s required,, nearly -5 mg* "being reached- "before the -eurro levels off* 8. 2ABLE 111 Collection Of 0l*3 A'- varying amounts of collector pH sain pie 8.5 5..02 tag. coll... .5 heads si.2 pH sample 4.0 5*00 mg* c o l l , .1 heads 5..02 *5 44*2 .3 65.G 5*04 1.0 46*4 .5 81*5 5*00 1.5 51*6 2.0 92.5 3*0 58.2. £5.0 94.5 5*04 5*0 65*9'. 4,0 9S»0 • 5 * 0 4 4 * 0' §6*-@ 5*0 95.4 5:»00 4*0 78 *-6 . 2.6 5*00 .66 91*0 • 5,01 S.O ' 77.1 .70 9s*e 5.01 6*0 74*5 3„0 5,00 00*7 5.04 5*5 • 71*7 *SS 88*9 5*01' 7.0 7 4 . 0 I h i s series .was' carried' out on hoth ores*. The .collector was fixed at 5 rag. «ncf was added' iiamediately Before Mowing* i l l ' samples mm 5 grams* -Salils 1? and Pig*. B give the resuit8 phtained with ore A* i SABES XI • Collection of C varying p H pH recover^' pH recovery pH recovery x~:us 94.?? 88.0 9.5 g- 94.4 6.5 90-.5 10*5 60 c 8 o n 95^0 6.5 9.1 e 5 10.5 G8.2 4*5 94*4 94.0 7 0 5 01.4 89,7 i i . n i i ,f) 27,0 4*5 95.4 0.5 73.7 12.0 4.24 5® 5 91.8 9.5 76.0 12.5 1.79 5?J» following reeiilts for Ore 5 were ob tained during the work 011 abstraction (see "below). After treatment with the rsanthate solution, which was f i l t e r e d o f f , th© ore was oividedjlnto spproalraataly f i r e grara sample.?. About 800 ml. of water was adaed to each and the pK was adjncrtod to that required. 2'hio was placed i n the c e l l , ''terpineol added, the T O I I M S was made up to SOO l a l * and the c e l l woo blown. X!ha;a the froth had cleared, both heeds and t a i l s were collected i n weighed gooohes and the scrapie weight was obtained by addition of the two weight 9 » RJ?he f i r s t s i s results i n the •cable are preliminary teste made on welched samples and treated as shown, and indicated that -this variation i n teehiiiqite { pre- vj&shlng with santbate } has no appreciable effect on the f l o t a t i o n y i e l d . Basnlts i n Table V awti Fig.4* 10 EABO ' ?' Collection of ore B - varying pH pl-l v/ash pH o e l l sample heads yj treatment 5*0 5.000 4.974 99.5 5 Bg. collector i n o e l l 7.0 5*000 4.928 98.6 do 11 #0 • 5,000 4.695 do O » •J 3*0 .5*000 4.975 99.5 ' prswashed with 5 ag. c o l l . 7*0 5.000 4.957 99.3 do 11.0 11,0 5.000 4.750 95,0 do. 5-..0 5*0 G»607 6.447' 96*5 . f pr swashed wl t i i 20 rag. 5.0 5,0 5.0 15 »0 4»S64> ' 4*200 6.243 .98,5 ) ssnthate -20 fjy.oie do 5.0 5.0 S.999 S,367 99. g do 5*0 &j 0 5.3.3 5' Be IBS 98«8 do 5 ® 0 .' # 0 4,864 4.754 97.8 do 5«-0 7*0 5.48? 5.202 .95.0' do 5,0 7.0 5.717 5*520 do 8,0 8.0 •4.315 4*212 • y / * o do IS . 0 12 .0 •4.970 3.684 74.1 do 12.0 9,0 0*644 • 6.344' 9S:*4 do 13,0 5,000 3..7-42 74.8 5- mg» collector i n c e l l ...... 5*000 .441 8*8 do * Another va r i a t i o n t?as made possible Iry the above technique* I t w i l l ho noted that several of the samples were "blown i n tb©. c e l l ' at a different pH to that at which they were treated with santhate, tn.it that this treat-, - -- "v . • M ' — *<*—  O o - m  si :o - > 1  k o DC %n  • : > t «w :D - > 1  k o DC %n  • : > t Pi > C ID - o > • ••• « * \ 11 meat seomlmgly has no ©ffeetsince the results agree within the experimental l i m i t s with the results of nor mal treatment* Ehis would appear to indicate i n a rather definite' -manner that whatever the controlling effect of pH- i s , i t exercises•that control during tho reaction "between the collector and the ore, and not at the attaeb.- '. meat "of- the mineral to the. a i r bubble« SecoapositlOB of Santhate As. mentioned on page2r decomposition of the atayl "xanthat© was expected i n the acid range, Snsyefor© i t "was rather surprising to fi n d tte collector "behaving 'very e f f i c i e n t l y - as f a r up the pH scale as pH l»{?ig«5)» "She decomposition talcing place "was followed by a method simil a r to that applied to ethyl'rant hate by Keraper (?}• • Samples of rcanthate solution with oufxer added, were adjusted to the desired pH, allow©a to .atana f o r 10 •minutes, then returned to gH:6«i>f ??hich seemed to work h©st„ -and t i t r a t e d electrOmetrlcally with standard -iodine- solution®, She- results are shown i n Sable VI and i n gra^h'fonii i n figure 5* ' • IS • fABLS ?I Decomposition of Xauiiiate mg» Xantiaate yl. Oxl ge f i n a l decosip. 1*6 .0099 .0004 9&VQ 2,0. 0 ^ 0 - .0004 96.0 2 .0' .0108 ,00051 '•95. S .0108 .0005 8*5 ,0104 • .0005 95.2 2.75 ,0099 .0005 :94.8 .5.0 .0099 .0018 81*8 s.o .•0099 .0021 •' 2..25 ,0099 .0056 6So7 Si 5 ,0050? • .00508 . •39.2 3.9 *0099 - *O081 18.2 -4,5 *00507 -.00493 2.75 •5*0 -.0114. .0112 ' 1.75 S.5 .©0507 ,00507 6»0 ; .0114 ." •00507 .00507 v0114 *0114 — - *0105 -.0105 ——— 13*0 «01o8 *01O3 Bftgeofr of Peooapogltlon In an offers to f i n d some reason f o r the higli recovery l a v & t j strong aeicl ptilp9 ta© following var-" l a . • S - Of, ... , , , „ . „ )ecompo s /tion of > - a.myl X awtlia.t'e. Le ft** ' A A ; .: ' 9e\ t • ' i , , . , . O : ; • • i • i y- '\J\J i f : — i \ . . . •• ...... . iations oa? f l o t a t i o n teehnig.ii© were introduced. 10 ml* { 5 iag») of the collect or were diluted to about 200 ml. s teffer was added and pH adjusted -as required. Shis Eiisctnre was allowed to stand for 10 iainntes, after which i t was poured onto the ore sample i n the c e l l * Serpinsol as added and the o e l l was blown, ffihis proaediirs., since i t allows the collec t o r to decompose aa ••determined above before i t comes in' contact wtih th © ore. should result i n a diminution of recovery, provided the prod- nets of decomposition are inactive as c o l l e c t o r s . A •few tests were made with axayl alcohol i n concentrations l i k e l y to be found,* with no collection rasttlting* and carbon disnlphids i n small amounts has no co l l e c t i n g ' • action* .It w i l l be seen from Sable • T i l .(a,b,e)» that t h i s Is the case, indicating-that any other possible products of decomposition have very little„ I f any, effect*. Bierefore . j , .the high, c o l l e c t i o n i n the strong acid rangej as Indicated on Pig,. ge. aiiat be due to the action of. the zaathate ' i t s e l f , Shorn f o r compasses atlve•purposes,• imowing the amount of teeospoaition {trow F i g * 5)* another few tests were made -adding the "effective", amount of co l l e c t o r present i n the above tests.' 2he.se are shown i n fable T i l {&,e)• She c o l * l e c t o r was added immediately before blowing the o e l l . 14 ¥11 Sffeet of decomposition on r e c o v e r pH 2.5 S.O 'S.5 a. Collector added (jug.)- 5.0 5*0 5.0 o. Eff e c t i v e -collector .225 1.0 8-7 e. Collection {#) 1* 6.08 39.9 • 92.S 2. 4.5 S7.2 a. Collector added _ .225 1-.0 2*7 ©. Collection (fl} 12*5 S9.8 88*6 At ta© sarao time another few tests war© made i n which the ore and c o l l e c t o r mid water were allowed to stand at a definite pB. f o r ton minutes "before a i r was admitted* Ehe rosnlte of two aneh testa wer© 94*6 at pE S and 93*7 ;f at gS 3*5* ihat i s , aliening santhat© to stand for ten minutes i n acid pE i n the proaenee of tho ors results •- i n only a very slight reduction^of recovery, .nowhere near that to he exp©eto& i f ths santliato were aooou- posecU Apparently, then, the ©rs coating, Br^pna'bly sine aayl scant hate is' formed ana remains, regardless of the pH* Ahj3tra^ion In view of the faot that potassium l»amyl santhate lias "been shmn to he d e f i n i t e l y effective "in f l o a t i n g hoth# samples of sphalerite used,, an .attempt was Baa© to show that the ore ttai».strseteart the c o l l e c t o r from solution. In the following worlc one sample B was used entirely* Previous attempts have bean made In th i s lab oratory to measure abstraction with sphalerite and ethyl scauthate with no success{14).9 the d i f f i c u l t y being one of t i t r a t i o n of the residual 2nanthate9 She general procedure followed wao to s t i r the ore with an eiccesa of sant.hate. i n solution for 10 rain, at the. required pH* fhe l i q u i d was then f i l t e r e d off the ore and attempts were made to fi n d either the amount of scant hate remaining on the ore or the amount remain ing In the l i q u i d * P i l t r a t l o n s ware performed with the arrangement described by Semper C7)-,9 except that the f i l t e r used wao a pyres f r i t t e d glass funnel of 10 cm* diameter* Several variations of'procedure were t r i e d as' outlined below* 1« She- f i l t r a t e was t i t r a t e d electroiaetrieally with standard iodine solutions . ffihis method, as found by other workers.,, gave results much too high, indicating either no abstraetica.,'or Indicating saore'reducing material i n the f i l t r a t e than had been placed there o r i g i n a l l y i n the form of .^anthato* She end-point was not good, the potential tending t o ' d r i f t badly, making the t i t r a t i o n very tedious and not very accurate. 2* .She f i l t r a t e was t i t r a t e d with iodine an before but using starch as Indicator* 'Shis gave high results also, and had the further -disadvantage that the d.isan%fe 16 thogen forced •o'bseured the "bin® starch color. S. Elie d r i f t i n g of potential in(l«) above seemed to indicate that tlx© reaction causing the interference was a slov? one. This .suggested the p o s s i b i l i t y of b-ack- t i t r a t i o n , carried out ciuicM.y, to remove the effect. M s was t r i e d by adding an excess of the iodine s o l  ution to-the f i l t r a t e and then 'bads-titrating with either sodium thiosnlphate or soSlitm arsenate,, again using starch indicator near the end-point, Ehls, however, gave a very poor endpoint.s the "blue color returning for'about f i v e minutes after i t hafi "been f i r s t reiaovod.s Atterapts were made - to standardise the end- point (such as. remaining clear after 2 ininntes) "trat t h i s vras not 'dependable* 4« She next l i n o of attack was to remove the scant hat® from tho ore and t i t r a t e i t . . After tho orig i n a l san- thate solution had 'boon removed., the ore was s t i r r e d f o r 45 laiiiutes i n acetone.. Tim acetone was than f i l % tered off,, diluted with water and t i t r a t e d . Using starch,- the acetone was.found to decolorize tho starch iodine coisples, while electroxaetriealiy, the acetone caused the potential to d r i f t so "badly that an accurate end-point was- impossible * Even after most of the acet one hod been removed by evaporation nnder a vacumm , these effects remained* 5* I t was noted that when sine amjrl saint hate was formed by addition of sine chloride to potassium• aayl" Kant bate solution, i t redissolved on addition of SOH*•' Shis suggested the po s s i b i l i t y • t h a t the ere coating eould. be d i s s o l v ^ i n 1C0H and thon the rasulting ^solution, t i t r a t e d . So t h i s end an ore sample,, after treatment with 2-anthate solution was washed thoroughly and thon s t i r r e d for giaours i n 2H KOH* Baylor and Knoll (6) state that under such conditions there i s esttsnslBe decomposition of xantfaate ion. One sample of san.tfe.ate solution was t i t r a t e d after being i n 2 1 KOH for S hours* /.It showed a decomposition of 6 !ps which could eas i l y be allowed f o r i n calculation of abstraction. . She WB solution was neutralized and t i t r a t e d , and after correction by a blank t i t r a t i o n , gave a result Indicating some abstraction* However as a eheMs on the refnoval of the coatings some of the or® was*- placed In the c e l l with, water and terpineol and blown* I t was found to f l o a t just as well, .as I t did before the KOH treatment* • Shis was taken as an Indication that the coating had not been removed* •Further indication of the permanence of the coating was obtained i n . an attempt to reclaim some x:anthate treated ore f o r further use* This ore was s t i r r e d for 10 hours In "2 IS EDI, after which I t was washed, thoroughly el u t r i a t e d and dried* A sample was .then placed In the o e l l with frother but no co l l e c t o r , when It was found.to f l o a t approximately 40 $ at pH 11. rlie characteristic flocculated appearance of the pulp was-••no ted, indicating that the floa t i n g was probably not just the result of cleaning* -fheoe results seemed to indicate that reiaoval of the rauihate layer, at any rate Quantitatively, was not p r a c t i c a l * I t was then decided to return to a% wore indirect t i t r a t i o n met hod• 6» SJayior and ICnoll(6) have given a method used by the-a i n a study of abstraction of ethyl Xanthate by galena* Since this was the pethod used to obtain the results "below i t i s given in d e t a i l . A weighed sample.of sized ore was placed i n a beater* a Imovm, amount of semth&t© solution was added* and after the addition of a few drops of atamontra?} acetate buffer, pH waa adjusted to that desired* Che aisrfrare ( t o t a l volume about ISO ml*.) was then s t i r r e d by motor for ten aiimtes. Ehe rant hate was Measured, by volume of a solution which had been standardised by an iodine™ starch titration.. At the end of the ten minute period, the l i q u i d was removed by suction i n the apparatus referred to abovo( -7)„ fhe ore. was washed with about 100 nil. of d i s t i l l e d , water and was then sucked as dry aa possible» She f i l t r a t e , which was perfectly clear, was diluted to 500 nil* i n a volumetric f l a s k . 100 a l . portions were taken by pipette and treated as follows: . ,; (a) t i t r a t e d as* i t was with standard iodine solution* 19 Co), a c i d i f i e d (pH 5) and extracted with S ,?0 »iU portions of toluene* Shis treatment ' remove ,e a l l santhate ae santhie acid (aolnhle i n toluene)» -She water solution remaining was then'titrated a f t e r neut r a l i s a t i o n * She volume of iodine tins obtained was subtracted from that obtained i n (a) as a correction for reducing substances present^othen than santhate* gho resulting corrected volume '' was used to calculate tho santhate remaining in solution and thus gave a measure'of the abstraction which had taken place* In the. f i r s t t r i a l of this net hoc!, two more 100 ml* portions of the f i l t r a t e were treated as above except that t i t r a t i o n wao done ei e e t r o a s t r i e a l i y . S i t r a t ion of .Cb)f was very unsatisfaotory and e n t i r e l y undefendable„* She reason was not determined- I t was also found "that' by using very,dilute iodine f -about -*3 grams per l i t e r ) and by adding,, as -.reeonmended by Eaylor and S a o l l , 5 a l * - of\. a ".5 K] solution of potas sium sulphate solution, a very exact ©'Mr-point 'eonld bo obtained using potato starch* {lot'soluble starch,)• Dilution of the 100 ml, portion of f i l t r a t e '-to about S00 Klv before titration-, so reduced the density of the d i ~ xanthogen foraed i n the t i t r a t i o n that i t s opalescent blue color dies not interfere with' the end- point blue* .Eesults obtained by this' method are shown i n Table f i l l below* A l l at pH 6-.0 2 0 3&BEB T i l l .Abstraction of 1-arayl.santhate by sphalerite (3) fest i!io 0 Or© At* Xanthate In Original P i n a l lag, Abstr. Abstraction mg./gr.-ors. 14 9*562 19*64 15.10 4*54 *475 15 | 347S 80*48 18 .02 2*46 . ,£80 16 4,70S 2S*S0 21,05' 2,25 *477 17 25.,SO 21 ..68 • 1,62 aS01 Averags -.408 fosts no» 1 - 1 3 were those uaed In methods 1 to 5 described'' above. One test, (Al8) was nan at pH 12*5 Instead of pH 6 with the result that an abstraction of *237 rao/gr. was foancU Alio reason for choosing these two values f o r pH'trill he found i n Pigs, 4 and 5 ...- pi! 6 1B well In the range of xnaadtacsa f l o t a t i o n , r/lrile i t Is not acid enough to cause decomposition* . At pH 13.5 recovery has dropped off sharply*One would expect „ then, less abstraction at pH 12*5* ffhls expectation Is borne out i n the results • above9. though In view of the. wide variation In results at pH 6, -one value at 12*5 cannot be considered conclusive.* Discussion of •abstraction results Fallowing the method applied by Herd (8) to galena, the- calculations below were Bade* Prom Stoltes Lsw9 using the average rate-of s e t t l i n g of the- particles as 12 cm. par minute, the average radius i s calculated to be 1»75 x 10 em* To check t h i s , a microscopic measure ment of SiO particles was made, giving the frequency curve shown, i n P i g . 6«4. where one square unit equals 256. square BJU. Calculation • of average area and radius frora the frequency table by a method due to l'hurstone(15) -S ,gave a value of 1,73 x 10 era. Area per etfoic centimeter of parti c l e s i s given "by the r e l a t i o n Z Area' equals volume x 0 as 1715 squ.ora. r Eaking the density of sphalerite as 4 gia./oe* gives the area per gram of 4-28*7 squ. osu Holaenlar volume of 97*38 .' -3S sine snlphide™m'^^^^ - 4.o4 ac 10 e.e. -8 Holecular' diameter then is S.4S x 10 . The number of Eiolecnleo per SQU»' cm* area, then Is 1 3*43 x 10 15 s *8S 2. 10 » She number of senthate ions then required • • 15- for a unimoleeular layer i s 1 ?7jgAlQ___ .. from Sable T i l l , , average abstract ion Iter gra® of ore i s •408 ag«. f i l l s corresponds to 23 , .18' •408 x 6*03 s 10 - 1.22 z 10 xanthate Ions* .202 2C 10 1'hese are spread over an area of 428*7 S Q U . era. fhe number of santhate ions per square era* then i s 18 15 ~J^?u-&-10~- = 2.84 s 10" . / ! O O D ~**™*~««*^**^^ ) oo • I t i s thus seen that the nuaber of nanthote ions abstracted i s suff i c i e n t to form a layer between one and two molecules thick. She calculations of area are .probably largely i n error, since the sphalerite particles' are estreiaely irregular i n shape, but the above result 'would seem to indicate a definite layer formation. SOTSAHY • 1. Behaviour of two different samples, of sphalerite with potassium iso amyl scant hate has been in v e s t i g  ated, both with oonoentratipn of collector and pH as variables •> 2® She decomposition of potassium iso ©ayl scant hate has been investigated. 3* Evidence i s presented concerning the behaviour of the senthate as a collector i n strongly acid: solution 4. i'he problem of abstraction has been investigated- and some results obtained* . • 11SP131HCS3 1. Gandl'n, "Flotation" p-204 MoGraw K i l l eo« 1932 2. 6.1.IUS©! Gttidie©, Eng., and Min* Jnl * p S58e 1935 5* Swainson and Anderson, Trans* "Sleet roehem. Soe* 60,S29,S1. 4* dark and Coz, A*I.M.I. 112,189,1954 5. ffavfc and Cos, A.I.M.B., 112§267, 1934 6. Saylor and l i o i r A j a l . S . 112, 582, 1954. 7. Kemper, 3*A* Thesis U.B.C'1940 8. Herd, M.A. S&esis, U.B.C. 1940 9. Bonnet M.A.Se. ffihesis JBB.C 1938 10. Candin, op*.eit. .p 37, 11. raggart, del Gnidioe, and iJeihl, A.l.M.B. 112, MB, 19g4. 12.. Saudln, op.oit. p IIS* 13. Balaton and Barker, Erans. .lleetroehea.. Soo. 60, 319, SI. 14. Hawkes, B.A.Shesis, TJ..B.G. 1940 15 e fhnrstone, "fnndaaentals. of S t a t i s t i c s " , quoted i n Stroud, "iMueationai .Psychology" p 73. 


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