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UBC Theses and Dissertations

Hydrogen peroxide as an indicator Handford, Freda Mary 1922

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nvdwft" 7 . fewx-'d-e an fc<t<i M*«f y*"df",°(   77 m H T D R O G f i K P 2 E O X I D 3 A S A I N D I C A T O R ?re-_ ::•-- -ndford A Thesis submitted for the Degree of MA3TS 07 ARTS la the Department of CHSIISTHT THS UNimSITT CF BRITISH OCLUKBIA April, 1922. g T. J 5 2 3 1921-1922. TE8 U3£ OF HTBROaM PS80XIBK ET A*U2DU3 SOLUTION AS AI COT3IB3 IXDIOfiJPOB XI VCL0MS2RIC ANAIYSIS. Last year (1920-1921) a considerable aacunt or ticie was a; eat on at toqptin~ to iaprove the mothod for estimating load vcl«motrical2ys by means of a Geclnornal solut ion of ^otassium dlchromate. not hoc! the load i s .>reoipatod from a neut ra l or o l i ;htiy acid solution IS 0 as load chromate whioh i s very insoluble (.00C02 _arto in ICO _-^rco E..0) The ifflirovement i-imed a t , consisted of t rying to find a su i tab le sab-stanoo to mar> the ond po in t . frcyicusJy an aqueous solut ion of 3i lve? n i t r a t o hid been used. Various compounds, such as sodium sulphide, ferrous sulphate, were t r ied but none of these yielded sa t is factory r e s u l t s . F ina l ly , an aqueous solution of hydrogen peroxide (3£) acidifiod with cone entr.-tod n i t r i c acid (1 par t in 100) w-a use J -a <*n outside indicator on a white spot p l a t e . The excess of potuysium. dicliromato solut ion irodueos a bluo color v i tL the drop of ind ica tor . "This blue OOE ound i s probably chromic ac id , " (Bosooe and Sohorlemmor,) according to Pdosonfold, ' when chromic acid i s in CXCOSQ, the blue color i s duo to the acid 1 GrOr and v/Lon hydrogen ^oroxidc i s in excess, to 5. o acid BjOrOp which although i t gives red s a l t s , i s i t s e l f (2) bine in oolcr , ' I Bias enfold, Be*-. 1908, 4 1 , 2826.) fh l determinations of load aado by the use of ^ r o g e n peroxide as the indicator seemed to be suff ic ient ly accurate to warrant further l nves t i -ga t ion , therefore the following work was done. Method of determining lead vo luae t r i ca l ly , T w i l l Sutton - iixtraot from Volumatrto i na ly s i s by Francis Sutton published by J&4 Churchi l l , London, 1911. "Bichromate method i lec 3 dichromate solut ion - .010S55 Pb. TS fhe following process for carbonate o r e s , pig lead arid special ly for red and white leads and l i t ha rge has been worked out by J.H.Wainwrlght." U.E.Y,ainwrlght, B. am. C.S. x lx , 389.1 "The necessary solut ions are potassium dichromate of such strength tha t loo repreeents about .01 gm. metal l io lead, not such BIO re or less standardised e i the r upon pure metal or on white lead which lias been ac -curately analysed for actual load by weight, s i l v e r n i t r a t e solut ion ae an outside indica tor not exceeding 2$ or 3$ in s t rength . "•-T:rop OF irROoaDPRai From 1 to 1.5 gram of o re , l i tharge e t c . , i s d io-solved in 10 to 15 cc . n i t r i c acid ( sp . g r . 1.2) the solution made s l i g h t -ly alfealine with ammonia and a considerable ey-cess of ace t ic acid added. I t i s then boiled and potassium diohromate solut ion in suff icient quan-t i t y to p rec ip i t a t e nearly a l l the laid i s run in from a bure t t e . The l iquid i s boiled u n t i l the p rec ip i t a t e i s orange colored, a f t e r which the t i t r a t i o n i s f inished, the f ina l point being indioated by contact with s i l v e r n i t r a t e as an outside indicator on a white p l a t e . " The precautions to be observed a r e j -^ h e solution of the lead s a l t must be as concentrate I U] as poss ib le and decidedly acid with -,c3tic acid* fhere must be absence Of o ther metals especial ly such as can ex is t in lower forns of oxidation Antimony and t i n , taxless ti-joroughly oxidised are pa r t i cu la r ly to be a-volded, Durlnr t i t r a t i o n , the solution should be kept as near the b o i l -i:.i.; _->oi*l Ml : .cs3iblc. Tho s t ron tL or oho OiehVMatfl solut ion sLouli. not vary much from that given above nor should the solution of s i l v e r n i t r a t e . " "In the case of dealing with ores containing small quan t i t i e s of s i l v e r , i t la des i rable to p r ec ip i t a t e t h i s before f i l t r a -t i on by a l i t t l e ITaCl so lu t ion ." 'The raothod i s specially su i tab le for such substances as white lead, rod lead, l i t h a r g e , o t c . Bed load i s dissolved by t r e a t -ing i t with n i t r i c acid and adding a d l lu to solut ion of oxal ic ac id , drop by Crop u n t i l the load onlde i s conrdctel^ disoolvco. If organio mattor i s prosont t i o solut ion should bo f i l tered before t i t r a t i o n . > h i t e load can bo dissolved d i rec t ly in -.cotio acid and the solut ion t i t r a t e d without f i l t r a t i o n except w! en --round in o i l* The method can also be used with ingot lead and al loys W t ^ t l t l m t i n and antimony but the sample must bo thoroughly oxidisod by repeated evaporation with funins n i t r i c c cid and the solution f i l t e red before t i t r a t i o n . " CALI3P..JT .10? OF JP-T. -JUS. >- •,IGT-T?S; The weights used for the following experiments were cal ibrated according to t i o method of T.W.Eiohards, (T.^.I.icharvs, Jour. am.Chati.Soe.g 1900, xx, p . 144.} :o Szzn.Cd.:X. . 01 f;. -CtUfcil i l l — . 0 1 ' " -.02 .05 .100 .100" .200 .500 1 2 1 2" 5 10 • 10" -20 -50 -w&i<?;it3. .0099 .0101 .0199 .0498 .0997 .0997 .1994 .4983 .9968 1.9954 1.9933 4.9835 9.9670 9.9670 10.9339 49.8547 C a l i b r a t i o n of graded 0 - 2 2 - 4 4 - 6 6 - 8 8 -10 to 1 00 10 '-Hi uc Us. . 0 1 " . 0 1 " * .02 .05 .100 .100 .200 .i>00 1 2» 2" 5 10» 10" £C JJ tJurotte a t 20°Ct \s &JTB8 0 . 9C70 .0099 .0099 .0198 .Q49C .0990 .0996 .1992 .^965 .9967 1.9954 1*9904 4.9855 - 9.9370 - 9.9670 - 19.9540 - 49.8350 The b u r e t t e tised was a . and i t was p o s s i b l e t o road i t t o 1 c o . 20 Weight of wa te r True each i n t e r v a l Cu^cl t .v 1.9242 sraras 1.9870 " 2.0480 " 2.0091 • 2.0297 • 1, 1, ,93 o c . ,y9 • 2 .05 • >. 2, ,01 • ,03 " Ei f forenco o? - r r o y tc ^0 -f-.CQOl ^ 0 + .0001 -f .0001 t .0002 to +.0001 to - . 0 0 0 1 - .0002 to ±0 - . 0 0 0 1 - .0003 Shel lbach one . ? r a e Tote-l 1.93 o c . 5 .92 * 5.97 • 7.98 • 10 .01 • (81 10 12 14 16 18 20 22 24 26 28 3C 82 34 36 « 88 40 42 44 48 48 - U - L, - 16 - 18 - 20 - 22 - 24 - 26 • 28 - 30 - 82 - .4 • 86 - 38 - 4 0 - 4 2 - 44 - 46 • 48 - 50 msfvffTB 2.0214 0 1.9750 " 2.0128 • 2.0449 " 2.0389 " 2.0173 " 2.0088 " 1.9910 " 1.9871 " 1.9391 • 2.0624 1.9998 « 1.9484 2.1269 ' 1.9836 2.0398 2.0245 2.0006 2.0010 1.9977 ojffljmftff SSi 2.08 M . 1.98 -2.C£ -£ . C L • 2.04 * 2,02 • 2.01 • 2.00 • 1.99 • 1.94 « 2.07 * 2.00 • 1.98 • 2.13 " 1.99 " 2.06 B 2.03 " 2.00 " 2.00 " 2.00 ' at* flr-turt 16°C. 11.04 M 14.02 " U .04 " 18.09 " 20.18 -22,18 • 24.16 " 24.18 " 26.16 " 80.09 • 82.18 " 34.14 " 34.11 " 36.24 " 40.28 " 42.26 " 44.81 " 44.81 " 48.21 * 80.31 " 1 . 9.9772 £Taas 2 . 9»9Tw4 8 . 9.9798 * 9.9971 oo. 9.9954 • 10.0007 • (6) 4 . I . ' . T. 8. dtii*tTIii 9.9661 graae 9.9781 " 9.9711 -9.9621 " 9.9816 " Ji!£. r 10.C070 ee . s 9.9990 -- 9.9920 " « 9.9860 " 5 10.0046 " Average 9.9986 ee . - amount of water delivered by p ipet te . The actual oapaoity in each oase urns found by araltipJyiag V **• footer given by Findley * to oorreot for temperature and bouyaney of a i r . (find lay, Praotloal Physical Chemistry) 3fAHSARIX;:^ l01f OP POTA33IUM DI0HR01UTS BSOnOBmAL 3CUJTI0H3. fho potassium diohromate uoed for those solutions was purified by making a boiling hot concentrated aolutioa of the sa l t and suddenly cooling* i t . The fine crystal* thus obtained were washed with redis t i l led alcwael and dried at a teaperature of 100°C. 9.806 grama of the r-urified sa l t were weighed and dissolred in 2 l i t r e s (2000 eo.) of d i s t i l l ed water at 20°C, thus aaklng a deoinomal solution with respect to the oxidation of iron in acid solution. Another solution was also node up. 14.71 g. of the purified potassium diohroaato were weighed and dissolred in 2 l i trai (2000 oo.) of d i s t i l l ed rater at 20°C. This solution was decincraal with respect to the precipitation of lead as lead ehroaate. Both solutions were standardised according to the ordinary pro-cedure, i . e . with Iron wire (99.7Jt Fe) carefully cleaned and dleselved In sulphuric acid excluded from. a i r . I?) 1. la) .if74- "V. ><Q required 32.16 co. II Cr C solut ion, 2 2 1 {b) ,221,7 ,, Fe required ^9.98 cc , K X r C solut ion, 2 2 V 2, ,1057 <> Fo - . i l l r c c i l r o 12.94 ec« oa.-aalra, ,.dcr_rota.ite so lu t ion . - crazlitgr calculated from, tho o-dLdatlon of tao iron. I'D) .2257 v. .097 ;: 1000 - .1009 nons i l i ty ?horofore 1 cc , or la ra t solut ion ia equivalent tc .01113 c« lead n i t r a t e or „CQ£9 f, lead, 2 . f1007 :: .397 x 1000 - .1500 n o r a a l i t j 53.64 r. 12.94 "I.horofor« 1 cc . cr tho second solut ion i s equivalent tc .01656 g« load n i t ra to c r .CIGCC r> le -d . vrx r.i-,\.C2 ::v ^4" .;r.T-T~. ?c',i\-ii..\., .The lead n i t r ^ t o noaa Muron^hotit t -cac ca oriueuia \v..s „>r_riflod in the aario va/ as tlio ^cta-acLou o3e!">ro_auto_ ?hr~e le-id n i t r a t e ec.-ations v.ore na.de. (1) $«1968 ~. load n i t r a t e wore dissolved in 500 co, distill©*, -.vtor, i . e . 10 cc , - ocxit-inod ,J_?L>9 ;> load n i c r a t e , (2} C.C179 -.. Iced n i t r a t e ,'£-_e dissolved in £00 cc . d i s t i l l e . afeer. i . e . 10 cc . cT t'.-j aclution contained .1364 y . load n i t r a t e . (3) 5.0345 ' . lo-.d n lb r - to \/oro dissolved in 500 co, d i s t i l l e d v-atey - t 2C°C. i . e . 10 cc . of the solut ion contained .1C0GS j» lead n i t r a t e . 2 J-SIT- "riT.-r.u- SCLL^IO^. 5.CG37 £, Carina n i t r a t e f i r s t / t r i f led "bg* ro= erj'afcallination were welched and dissolved in COO cc . d i s t i l l e d ^atey a t 20°C. w yLltyTChfn 'J?wo indicators ware used, lydrosea peroxide solut ion, s t rength approximator £$? but actual ly 2$G determined by t i t r a t i o n witfe potassium i ernanyanate so lu t ion . 10 ee. of the aqueous hydrogen peroxide solut ion V'IS mado u^  to contain .1 cc . concentrated n i t r i c acid* Th© other indicator used was an ^quoous solut ion of s i l ve r n i t r a t e of several dif ferent concentrations mtdo u. ex-ctly by Vvoi' h t . jrT\0C^ru7cJ; Ten cubic csntimotors of? an aeneous addition of loo.d n i t r a t o was measured by mo^ns of a cal ibrated j i p o t t a into a 150 cc. boaterj the solution heated to bo i l ing , approximately tL^ rocuiro ' number of c c ' s of potassium dicbroraate solution ran in and tho mixture boiled to coagulate the lead chroiaate. ?ho t i t r a t i o n was then f inished, the end-joint beiac i n d i c t e d by the use of HgO., or j2gB03 as an outside indicator* SojulSs cf e i t r - t ions ; ardro-en - roxiJe uaod a3 indica tor . So, cf cc . K^CrgC^ s o l . u 2 . 3 . 4 . 5 . ft. ' . ° . 1, 10 , 1 1 . 12 . U«l 11.1 11.0 u.i 11.2 11 .1 11.15 11.15 11.1 11.1 l l . l 11.05 11.0 .025 c c . « • i H »1 ;• •1 : l" n n n n B u r e t t e 11,125 11.125 11.025 11.125 11.225 11.125 11.175 11.175 11.125 11.125 11.125 11.075 11.025 c o r r e c t i o n -- . 1 c c . « • 1 w m t» 1-•< •t n n t i n rb(lTC 5 2 c a l c u l a t e d . .1227 fa .1227 " .1224 • .1227 " .12SS (* .1227 • .1252 • .1227 • .1227 " .1227 • .1221 " .1215 w 19) Kosrlta of titrations* qrdrogoa peroxide need a» Indicator. Ho. of co. K2Cr2°7 8 0 l # Burette oorreotlon Pb(B03)2 oalonlatad. 14 . 15 . 16 . 17. 18 . 19. 2 0 . 2 1 . 2 2 . 2 5 . 2 4 . 2 5 . 2 6 . 2 7 . 26 . 2 9 . 3 0 . 3 1 . 11 .1 11 .1 11.05 11.0 11.15 11.05 11 .1 11.0 11.2 11.1 11.05 11 .1 11.1 11.0 11.2 11.0 11.05 11.15 .025 0 0 . t l < • , :• !> T» t l 11 It I" It N It It f! 1! II " average 11.09 11.125 f 11.125 11.176 11.025 11.175 11.025 11.125 11.025 11.225 11.125 11.07B 11.125 11.125 11.025 11.226 11.02F l i . f f B 11.176 CO. s .1225 g . - . l c c . t l • . : i t n t t if i i if II II i» II ! l It t l II .. laad n i t r a t e . .1227 .1227 .1221 .1216 .1232 .1221 .1227 .1216 • 1236 .1227 .1221 .1227 .1227 .1215 .1238 .1216 .1221 • 1232 /.Otual aaotdt in 10 cc. - .1239 g* load nitrate. # Correction for indicator. .1 oc. was deducted for error caused by the indicator; this amount was determined by a blank titration. In the following series of experiments hydrogen peroxide was vsed as an indicator. 116} •burette, Pol'JD^K Corgectioao, o a l e x i a food« 12,59 ceo ',; - . I c e . ,1567 g , 12.34 " " .1CG2 !t t 12.54 • " .1262 " 12.15 " " 12.19 " " - ^ - S " i 2 . i 4 • • »1M« • G. 12,25 " " 12.29 • .W§6 12 . 54 " " .15C2 ; 1 2 „ 4 • * .1 -62 *' 12 . •oC • * .1562 , 0 . l i d ) " " 12.S4 - " .1362 * ? B o, 12.<\5 12 .3 JL2, • 5 1 . - - O -1 2 . 1 12 ,3 12 .5 12 .3 12 .3 12 .3 12.4 12»<^ 12.3 12 .4 12.30 £2.25 12.2 12 . 3 12.4 TO • l^A. 2° 7 c e . » w ". n n M f j « • rl n w v tt ! • ; r r If n » J?iL2£» s o l u t i o n . .04 CG «i • « * « N i t «. *» * N i t i t »» 0 i t it »• i t i» 1 1 . " * 12.34 " • » « • ' 12* • * 12.44 " .1273 ° ID, 2 .3 • " 12.L4 " • .1-62 " K . * f 12-S4 " .1-62 " 1 C o .  " " 12.44 " " .1375 16 . . 5 " * 12.39 " .1^67 ' 1 7 . 1 " " 1 2 . 2 9 • .1-56 I S . 5 " " 1 2 - 2 4 " " •***• 1 3 . .5 " " 12.34. " " .1-62 20. ' " 12.'=4 " " • * « * AT.rase - 12.5 + .04 - 12.54 - . 1 oe* = .1562 j . l M ^ ) 2 ctrarvl aoorab of leccl nl fcr- to i'o 10 c o . a,niocT:a s o l a t l o n woo .1564 r . :• C o r r e c t i o n Tor i n d i c a t o r . I n t h e fo l lowing a o r l e s or or-orlffionts, l y J ro en - . r o ^ l d o w.s USG3 : a t n I n d i c a t o r . I T , , -?-; l,:^ipTpuai% l« 2 . «?• ' : . r 6 . 7 . e. c. IC . 1 1 . 12 . 1 0 . U . I f . 16 . 1 7 . i e . 1 9 . 2 0 . , Corroc ivorajjo CttiSl fl Tit t i b n ivs "TV* . i o t a s a j G.2 G.00 G.2 6.2 6.15 6.2 6*2 6.2 6 . 1 6 . 1 6.2 6.15 6 . 00 6.25 6*00 6 . 1 6 .2 6 .2 6.2 6*2 St. JSBL -IJICQ fey iuOio 6.1C eo» -.mount i n 10 ; r a t i o n s w i t . u u ce r J. an indioi t o r . CO*,3 Of u!oi : ro&: te . .03 o c . H t» n n n M n « «t N w »l « H « « » It fl J. t o r . ^ a r e t t COXTOO'G 5.17 # b .97 6.17 6.17 6.13 6.17 £>»B7 6.17 6.0'? 6 .07 6.17 6.12 3.97 6.22 £ .97 c?.c? 6.17 6.17 6.17 6.17 ce„ - .10063 - , loacl aJ ejf s o l u t i o n x .i v.-.r-/aco-t;d s i l v e r .10069 L» ; lo^i t t n lo . ? : ) ( ? ! 6 s )o c a l c u l i u^ . - . 05 ) .1013 g . " .0980 " » .1013 • •• oioac » » .1006 " » .1013 • " .1C30 • • .1013 • »» .0996 • • .0996 * t! .1013 " • .1001 '•' .0900 • * .1021 " • .C9G0 " " .0936 '•" • .1013 JC M .1013 " ,1012 " " .1013 • t . a id n i t r v t e . n i t r a t e s o l u t i o n 12JJ ooncen t ra -118) so. or 1 . 2 . 5 . 4 . 5 . 6 . i • B, 9 . 10 . 1 1 . 1 2 . i s . ^P.f..iffA .9A8 ff.f K 20r 207 12 .V .04 ee« 12.6 u 12.G « 12 . £5 • 12.G • 12.6 11.2 .026 OC 11.0 " 11.2ft * 11.25 " 11.2 • 11.2 • 11.2 # C o r r e c t i o n f o r i n d i c a t o r . V 1 CO, c " The f i r s t Averaeo was .1364 too h i g h . amount -Burette. c o r r e c t i o n . 12.74 # 12 . fit 12.64 12.69 12 . 04 12 . 04 | i l o i j i i j 1 n ".on 11.275 11.273 11.225 11.225 11.225 (-»C5cc M • ft • • t f H If T n „ ' K 2 C r 2°7 s c l e t i o n s . C l l i r 2* lo^c n i t r a t e . s i x dosorciinatioris a r e a l l .KG; > .'.otual ^.lotait of bco foi^L. r n ( ' ) 0 B ) 2 i n 10 oo . . >.) of i > , e r r o r BJ-X too hi--h, La i t seven dot eraiaafc ions A v e r s e .124? <> ^ ( r O ^ J g .1229 g . P b r i C G ) 2 . -'JI jfctocat v»u a_dc t c deters*-ue t b o i r ' j r asenoe . Al l f a i r l y i n s o l u b l e c I c i u n , e x i s t i n g , i n 10 GCe what iaetals of aeneous 'M-'O, L .1412 £• .1400 • .1400 " .1406 " .1400 « ,1-00 « ,1243 « .1269 n .1249 • .1249 n .1245 '' .1245 * .1245 • » • s o l u t i o n are a l so s o l u t i o n would i n t o r f e r o by ohroaatos such is a: mercury, v. 'ill of eourso i a t o r f o r o . JLso in lower forms of ox ida t i on t i n arc"1 aatiEorcjr. A nunbor of de t e rmina t ions wcro such ^,s i r o n eude i n bio j Llvorff b a r i u n , a l l meta ls capable 0"7 i a t 5 o f e r rous s t a t e , •rosence c i s i ne i n un varying amounts and in no case did the zinc upbear to have tho s l igh tes t offeet on tho end-point. I ron in the f e r r i c s t a t e lias a marked influence ^roventlng t y the oolor i t ,^.1\:'7 -' the »olution >.•/.:•:; nafcisPector; end-point be in:; obtained. •1040 g . f e r r i c n i t r a t e dissolved in 10 cc . or t l » aqueous eolat ion of lead n i t r a t e prevented any sa t i s fac tory dotsra ln^t ion. Mnart of iron .0144 g . • »23$ by weight in comparison with lead . x?-r^i::.?ic"-: »• av IT? ^ : _ - . ^ C . cr -MEO, The aino was woiijhod in the fora: of .sine nits r a t e and dissolved in 10 cc . of the aquooua solut ion of load n i t r a t e and the solution t i t r a t e d in the usual Banner. AS zinc n i t r a t e i s d i f f i cu l t to purify -nd i s d s o very deliuaoscont, the aoounta cf 3lnc arc only «_pproxlnute» In the follow! a;; s e r i e s , lydro^on peroxide was used as an ind ica tor . :o. of oc. rc0r2 ' :7 12.4 c c . • j o i n Urn . • 6 .1 " e . i »• 6 .0 " 6.0 • 6 .05" 6 .0 • 6 . 1 " cu re t t e . c o r r e c t i o n . 12,^-4 c c . 12,14 M " .00 • 7.98 » 5*98 " 5.98 " 6.03 • 5.98 w 6.05 " I n d i c a t o r c o r r e c t i o n . 1 - . 1 .. « i H .« A n o CC.) Pb(iro J v;cit;heu. • 156£ :; . .1564 « .1564 " .1062 * .1006 rt .1005 " .1006 • .1006 " .1006 " ?b( I I0 0 } 2 o^lculaSec!. .1575 r . .1542 " • 1512 • .1512 " •G98C » •09GC " .C99C • .0980 • .1996 rt of - i n c . 100?' w$ sqf 70£ 30 70, 105/, 140,. loco'. Detorxinrtiona of load in more concentrated so lu t ions . In tho following experiaenfcs, the anounts of lo^d n i t r i t e carefolly L ur i f i ed , v/ci-i cd and c'isoolvoc' in 10 cc . d i s t i l l e d v a t e r , then t i t r a t e d in tho t») usual manner. ••cb. of . 1 *w „ , \ j \ H 6 .sooo n .4000 " .1000 « .2000 " .5000 " »B0M .2000 " •8000 »' .4000 " .5000 • .6000 • .7000 " ' .6000 • .7000 • 0 . o •* c c . A 2 "^ •? 1C.1 GO. 27 .1 * 36 .0 • 6 . 1 " 12.16 " 30 .2 " 18.2 " 12.2 " 19.9 • 2i> »*3 3 0 . " 36,16" 41.35" 36.00" 4 1 . 9 • 2urc'«to correction 18.19 cc. 2 ? . 2 y c 36.11 * COG " 12.19 30.29 • 18.29 • 12.24 " 17.965-23.655" 30.09 " 36.26 " 41.605" 36.11 !* 42 .18 -Indicator C£^C0tigXi9, - . 2 oc . 25 -.Jc5 - . 0 5 - . 1 - . 2 - . 1 - . 1 - . 2 - . 2 - . 2 - . 3 - . 2 - . 3 : ; • • ) l IT I . '! M H 1 1 »» H (. H 'jst. o r e~ I cu la t eoe .2002 ,„ .^ccc '• ,3991 • .0996 ' •2CC1 .4966 -.2993 • .3010 -.2973 ,? .; :o: .4949 " .5971 • .5CCJ " .5946 " .6935 " I t w i l l be observed t7 t - • -' ounccntr t i cn of tho load n i t r a t e solut ion la increased the r e su l t s buooc^. tec lov. concentration of X-lead n i t r a t e apparently gives the beat r e s u l t . Acoordin 2jr ch^roforo varying amounts of lead nltr&ts were dissolved in such amoi-nts of d i s t i l l e d water t* x t: ~ solr.tiO'is woro _>:.>_ roximate'ly 1?. in concentration. 2bat l a , .4 g, Pb(iiCr,)2 Wws dissolved in 40 cc . d i s t i i l o J „~tar . In each of the followin/j de tcra in- t ions a bl^nl V/.-J uudc so dstucv&ne the correction "or i 'c Indicator , I . e . ITJCTO ,on . «ro:d.de so lu t ion . JO. ruuoous s i l v e r n i t r a t e soltition % cono. wis .;<.leo us as' to dot amino tho c.id-. oint and in no c so -,-3 - - o:id- ci„it fo nd at tl 'e s-mo . ' 'radiation. I (16) ,COi:6 • ' . 2^.4- 34.06 c c , - ,H t i , . ^ G , .5000 " £0 .4 - 0 . 4 9 " * .S • .4999 " .6011 " 56 .55 <76.C6 " - . 4 " .6004 " .7004 " 42 .65 <-Z.% " - • < " .7009 • .50C0 • 30 .40 20.*:9 " »«3 • .« 999 " .4010 • 24.25 24 .41 « - . 2 " . 4 0 0 9 " .6015 " 5«*6 - 6 . 7 6 • - . 4 " . « * U t: .7004 " 42 .55 42 .85 " - ,C " .6992 c! .5055 " 50 .7 i.-0.?9 * - . 5 « .50*9 " .4057 n 24 .5 2^ .46 • - . 2 • .4017 n I n tl '030 de t c r t rda - t i ons t h o e r r o r i a no t c r e a t o r tLn& $ • axnibor of d o t o r t i i o ^ i x i g i/oro :.i.f;o on l^.. f f o i l . :Aeco of lc~d was e c r o f v l l y sc ra^sd end claAn<*3,tl:on jo£;,,,ad. I t v/i,s t hen d i s so lved l a 20 c c . i i i t r i o wCifl UC c c . cone . liter, + 10 cc I"«X) \r I c o t L : ; . fLo s o l u -' tior.. wao J v s t acv. t rei ioat . v.ltl-> raraonlum :#aro.£ide, t b s a -.eidtCiod vitfc a c e t i c a c i d . Tho solvitioi:. \ /as t'-oii ixx.tcd t o b o l l i x , and t i t r - t a 3 i n t l io i-3-ce.l *3nnacr. "bo j ^ - ^ t of s o l u t i o n v/o.a kep t approximately e o n a t u n t . 7 o . or o c . b u r e t t e lad l e c t o r - a t . of F ? Cr ? C 7 ocgyco t ioa . c o r r e c t i o n . J l S ^ solut ions . . S ^ A S M S ^ G.I ec» 6.08 co» - . 0 5 ec« .0^25 , ; . «« 7.5L " 7.£5 " .0755 " n 6.2 • 6.10 " .0655 " 6.0 rt 5.9G *' .0615 n n 8.1 • 8.08 " o • * 8 e " 21.05 » 21,19 » " .2197 " M 24.15 • 2- . .31 " .2521 • «t 22.8 E - 25.0 " .25CD ' (16) lead relghed-•1641 g . ,3478 • •3440 * ^tfi Of M» X20r2C7 joisHflL* 14.4 oc. 22.6 " 32.8 -»rretlg»> 14.42 ee . 32.66 " 32,66 " jLlas* o - .06 ee. .1604 g . •3367 " .3367 -From theee results i t w i l l be observed that ae the solution of lead be-comes more ooneontratod, the results calculated from the t i trat ions ehow a considerable negative error* In the following series of experiments, an aqueous solution of s i lver n i trate . 2gjG concentration, was used as an outside lndioator. The weighed amounts of lead nitrate were each dissolved in 10 oc. d i s t i l l e d water and titrated as usual. The end-point was indicated by the dark red precipitate produced by ths drop of potassium diehromats solution with the drop of indicator on a white spot plate* Burette imt. Pb( 10 J 2 correction calculated, 31,32 CO # (f*06 00*) ,6178 g , 30.78 • « .6090 " 21.12 - - .6163 • 43.36 " " .7170 " 42.48 - " .7134 • 43,76 " " .7236 " 37.67 " • .6221 " 37.32 • • ,6180 • # Correction for indicator, The oaloulated amounts are a l l about 2-3J, too high. This may be duo to the fact that the red color of s i lver ehromate i s very di f f icul t to distinguish in the preeenoe of lead ehromate whieh i s orange in color. t . pbdo 3 ) 2 wei/tfod. •6086 g . •6016 • ,6063 " .7060 " .6996 • ,7034 " .6003 " •6011 • soJaUsA* 31.2 ca* 30.7 " W.O " 43.1 * 42,2 • 43.6 B 37,4 " 37.16 • (17) In the blank teat it was found that 1 drop of ;otassluw dlohrona ta solution or .06 oo. in 30 to 60 oo* of water will produce a very p*ruep-tibla rad oolor with tha drop of eilrer aitrata Indicator in tha abaanda of tha orange lead ohromate ireolpltate* MiWBfTIT? "f "TT^ BIT tiff i It wua thought poaslblo to use the hydrogsn peroxide lndioator to de-termine tha and-point of tha reaction in the oxidation method"of deter-ainlng iron* Owing to tha strong oolor of tha eolation, thia was Jnand quite inproetloable* An attempt wan anna to estimate eilrer and aerlun in eolation a/ pre-•Ipltating then ae ohronataa and detamining tha and-point by uaing tha hydro r«n peroxide Indicator* It waa dleoovered that both ailrer and barium ohronate dissolve in tha drop of indicator and so prevent amy and-point being found by this act hod. O01OU3I0B3I f ha foregoing results show that tha hydrogen peroxide lndi-oator gives more aocurate results than the aqueous ailrer aitrata solution for dilute solutions of lead. That when the eolutlona of lead are concentrated, the results obtained by using hydrogen peroxide as the lndioator are too low* That quite aocurate results can be obtained by tha use of hydrogen peroxide as an Indicator If the solution of lead nitrate i s ncntjaora than 3$o concentration* BI3AUTAWAffiS3i A large correction i s necessary for the indicator* i t ia •1 oe of potassium diohromate solution for every 20-25 on* of the solution in the beaker whan the titration la finished. This corresponds to *001 g* lead* The end-point la difficult to detent without preotlen einae only n pale bine oolor la presumed* 

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