NHNG IM CN CH KHI LM VIC TRONG MT PHNG THC NGHIM HA HC I. Nhng c tnh cn thit ca cn b kim nghim Cn b kim nghim lm cng tc phn tch cn phi c mt s c tnh c bn sau: - cao tinh thn trch nhim, yu ngh - Trung thc, tht th trong cng tc. - Thn trng nhng khn trng - Kin nhn nhng linh hot - Chnh xc, tinh vi - Trt t, ngn np - Sch s, gn gng - Ht sc theo ng k thut quy nh v k lut lao ng. Thiu mt trong nhng c tnh ny, ngi k thut vin c th c nhng s liu thiu chnh xc nh hng ti kt qu phn tch, kt lun v nhiu khi gy thit hi n tnh mng ca con ngi v kinh t Nh nc. II. Ch lm vic ca kim nghim vin Ch lm vic ca kim nghim vin thng chia thnh cc khu vc sau y: - Khu vc phn tch ha hc c bn , gi cc dung dch, ha cht, thuc th, t ng dng c v t ng ha cht - Ch ngi ghi chp kt qu. - Ch ra dng c, chai l. - Phng cn v dng c, my mc vt l, cc loi cn (cn k thut, cn phn tch...), cc my mc vt l. - Phng ht (hotte) c qut ht cc kh c lm nhng phn tch, nhng phn ng sinh hi c, hi hi hm Nguyn tc v ni quy trong phng lm vic: - Vo phng lm vic phi mc o chong (blouse). - Phng no dng cho vic y.1

- dng v ha cht phi ng ch quy nh. - Thit b dng c dng cho vic no ch c dng cho vic y. - Phng cn v dng c my mc vt l chnh xc phi c ni quy ring: + Phi c h thng iu ha nhit , gi m, nhit theo ng quy nh khng nh hng n my mc. + Ch c vo phng cn khi cn hoc s dng cc my mc vt l. + Ra vo phi ng ca, trnh lm nh hng n m trong phng. + Ch dng nhng cn hoc my mc c quy nh. + Khng m my, vn nt nhng my mc khng thuc phm vi s dng ca mnh. + Khi s dng my mc phi theo ng quy nh s dng. III. Vn bo h lao ng Mi thao tc phng ha hc phi lm vi tt c s tp trung ch v suy ngh. Lm khng suy ngh c th dn n nhng tai nn thit hi cho bn thn mnh, cho ngi khc v cho cng vic chung. 1. Ht sc trt t, ngn np, sch s, gn gng trnh nhm ln, gy tai nn lao ng v h hng. - Trc khi dng phi c k nhn hiu. - Dng xong phi tr ngay li ch c. - Dng c dng xong th phi ra ngay. - Khng dng dng c th nghim n ung hay ng thc n. 2. Phi theo ng thng quy v ni quy. Ngoi mc ch bo m kt qu chnh xc cn trnh nhng tai nn c th xy ra. 3. Ht sc thn trng trong cng tc: a. Tin hnh mt phn ng c th gy chy hay gy n, tro hay bn ra ngoi, phi lun lun bn cnh v nm vng nhng nguyn tc x l ty trng hp. b. Khi lm vic vi cht d chy, tuyt i: + Khng dng la ngn. + Khng lm vic bn cnh la ngn.2

+ Khng cht d chy bn cnh ngun sinh nhit (cht d chy rt d bc hi c th lm n chai l hay bt nt. Hi bc ra gp ngn la s bt chy, ngay c khi ngn la xa). + Trng hp b ra ngoi, nn thm kh bng gi v a ra ch thong cho bay hi ht. + Trng hp b chy khng hong ht, nn bnh tnh dp tt ngay bng chn hay ct (nhng cht nh eter, xng, benzenkhng tan trong nc, li nh hn nc v ni trn mt nc, khng h dng nc dp tt khi chy c. Nhng cht nh natri, kali, kim loikhi gp nc s sinh hi hyro d chy, nu dng nc dp tt li lm chy thm). + Cht d chy phi c kho ring, phng lm vic ch gi tht t, dng. c. Khi lm vic vi cc acid v cc baz mnh. + Trnh khng ra ngoi, phng bn vo mt, tay chn, qun o. + Bao gi cng acid hay baz vo nc khi pha long (khng c nc vo acid hay baz). + Sang chai phi dng phu (khi rt ch quay nhn ln pha trn cn chai kia trn bn tuyt i khng cm tay) + Khng ht acid hay baz bng pipet khng c bu an ton. + Khng ht bng pipet khi cn t acid hay baz trong chai. + Nn dng cc loi pipet an ton nh pipet bm ht, pipet c bu cao su + Khi un si, phi cho bt, mnh thy tinh hoc bi thy tinh iu ha, trnh bn hay tro ra ngoi. + Trng hp acid c b ra ngoi, cho nhiu nc lm long, di k v lau kh, sau phi git sch gi lau (nu dng gi lau ngay, gi s b mc v nu khng git ngay gi, ngi khc cm vo s b hng). +Trng hp b ra chn tay, di ngay vi rt nhiu nc lnh, ri bi ln ch b bng dung dch natri bicarbonat 1% trong trng hp b bng acid, v dung dch acid acetic 1% nu b bng baz.

3

+ Trng hp b bn vo mt, di mnh vi rt nhiu nc lnh hoc dung dch NaCl 1% (ngi b tai nn nm thng trn bn), y bng bng sch v a ngay n bnh vin. + Trng hp b ung phi vo ming hoc d dy: - Nu l acid, sc ming v ung nc tht lnh c magi oxit. - Nu l baz, sc ming v ung nc tht lnh c 1% acid acetic. - Trong c hai trng hp u khng c cho ung cht lm nn. d. Khi lm vic vi cht c: + Cht c chia lm hai loi: Loi A: gm cc cht c gy cht ngi v cc cht c gy nghin. Nhn cc chai ng cht c ny nn trng vin en, ch vit en. Loi B: gm cc cht c nguy him: nhn cc chai ng ha cht ny nn trng vin . + Cht c cc loi u phi trong t ring bit, cha kha do ng ch trng phng gi. ng ch trng phng c trch nhim theo di khi a mt cht c ra cn cho n khi thu hi v. + Cht c sau khi cn, phi pha ch ngay, ng vo l, vo ch ring v dn nhn nn trng c gch en pha di nu thuc loi A v nn trng gch nu thuc loi B. + Ht cht c nn ht sc thn trng + Trng hp b ng c, lm nn tht mnh, tht nhanh, hoc cho ung nhiu sa, lng trng trng (trng hp kim loi nng). e. Khi lm vic vi cc thit b dng c c in: + Tay phi tht kh, ch lm vic cng phi tht kh, trnh m, bn nc hoc ha cht vo my. + Kim tra k in th ca my trc khi cm in th 110 volt hoc 220 volt

4

+ Trng hp xy ra tay nn, nu ngi b nn chm vo dy in, tt ngay in hoc rt cu ch v ch chm vo ngi b nn bng nhng vt khng dn in. Tin hnh h hp nhn to ngay vi ngi ang b ngt. g. Khi lm vic vi dng c bng thy tinh, s: + Ht sc trnh v. + Dng c loi no dng cho vic y, ch c un nhng dng c dng un v dng cho chn khng nhng dng c c bit dng cho vic ny. + Trnh dng dng c rn nt. + Trng hp b t tay, phi tm ly ht mnh v v x l mt cch v trng (bi thuc hoc cn iod) + Trng hp b mnh v bn vo mt, bng ngay vi gt sch trnh con mt di ng nhiu, lm mnh v d vo su trong mt, a i bnh vin ngay. h. Khi s dng hi t: + Khi m kha vi hi t, phi chm la ngay, trnh hi t trn lan khp phng. + Khi khng dng, kha hi t ngay, kha tht kn. + Trnh gh mi vo gn vi hi t. i. Khi s dng ht (hotte): + Phi ng ca ht trnh hi c trn lan ra phng. + Phi m l thng hi, hoc qut ht gi a hi c nhanh chng thot ra ngoi.

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MC TINH KHIT CA HA CHT V TIU CHUN S DNG Ty theo mc tinh khit, cch s dng cc ha cht cng khc nhau: - Loi c bit tinh khit dng cho cng vic khoa hc c bit. Loi ny ch sn xut khi c yu cu c bit. - Loi tinh khit phn tch (loi nht) m bo cho cng vic tin hnh nhng qu trnh phn tch v cc cng tc khoa hc chnh xc. - Loi tinh khit (loi nh v ba) c dng trong khi tin hnh nhng cng tc thng thng ca phng th nghim, hoc i khi trong cng nghip, khi cn tinh khit tng i cao trong sn xut. - Loi k thut c dng trong cng nghip. Bng tm tt chung mc v k hiu tinh khit cc ho cht theo mt s nc Mc tinh kht c bit tinh khit Nht Nh Ba Loi k thut Lin X CO Specialement pur CP - X P.P.A - A p- Tex G.R.S G.R P - CP Techn P.P.A CP P Techn G.R - PA EP P Techn Nht ng Nh ng Tam ng Cng nghip Tip c Hung Trung Quc

Bng nguyn t lng ca mt s nguyn t Tn nguyn t Antimon (Stibium) Asen Bc (Argentum) Bari Bimut Bo Brom Carbon K hiu Sb As Ag Ba Bi B Br C6

Nguyn t lng 121.75 74.9216 107.87 137.34 208.98 10.811 79.909 12.01115

Cadimi Canxi Ch (Plumbum) Clo Coban Crom ng (Cuprum) Flo Hiro Iot (Iodum) Kali Km (Zincum) Lu hunh (Sulfur) Magi Mangan Natri Nhm (Aluminium) Niken Nit Oxi Phospho Platin St (Ferrum) Scandi Selen Silic Stronti Tantali Thic (Stannium) Thori Thu ngn (Hydragyrum) Titan Urani Vanadi Vng (Aurum) Xeri Xezi (Cesium) Ziriconi

Cd Ca Pb Cl Co Cr Cu F H I K Zn S Mg Mn Na Al Ni N O P Pt Fe Sc Se Si Sr Tn Sn Th Hg Ti U V Au Ce Cs Zr

112.4 40.08 207.19 35.453 58.9332 51.996 63.54 18.9984 1.00797 126.9044 39.102 65.37 82.064 24.312 54.9381 22.9898 26.9815 58.71 14.0067 10.9994 30.9738 195.09 55.847 44.956 78.96 28.086 87.62 180.948 118.69 232.038 200.59 47.9 238.03 50.942 196.967 140.12 132.905 91.32

7

N V O LNG V K HIU Tn n v Kilomt Mt ximt Centimt Milimt Micromt Mt khi ximt khi Centimt khi Lt Mililt Microlt Kilogam Gam Miligam Microgam K hiu n v di km m dm cm mm m n v th tch m3 dm3 cm3 l ml l n v khi lng kg g mg g Gi tr 1000 mt n v c bn 0.1m 0.01m 0.001m 0.000001m hay 0.001m 1 phn nghn ca m3 1 phn nghn dm3 c dung tch bng dm3 1 phn nghn ca lt 1 phn nghn ca ml n v c bn 1 phn nghn ca kg 1 phn nghn ca g 1 phn nghn ca mg

TM TT CCH PHA CH CC DUNG DCH CHUN DNG NH LNG

8

I. i cng cch pha ch cc dung dch chun Mun pha cc dung dch chun, c th dng cc phng php sau y: 1. Pha thng t ha cht tinh khit. Cn chnh xc mt lng ha cht tinh khit nht nh, cho vo bnh nh mc, ha tan bng nc ct, sau thm nc ct va n vch, trn lc u. 2. Pha dung dch gn ng ri chun li (i vi cc ha cht khng bn). Cn v pha mt dung dch c nng cao hn nng cn thit tnh theo l thuyt, sau xc nh chun ca dung dch thu c theo mt dung dch chun mu, hoc bng mt lng cn chnh xc ca mt ha cht khc tinh khit v vng bn trong khi bo qun. 3. Xc nh h s hiu chnh F: Nu nng thc ca dung dch khng ng vi nng l thuyt, phi tnh thm h s hiu chnh F i vi chun ca dung dch pha ch. Thng ngi ta pha dung dch chun c nng cao hn l thuyt mt cht, v th tr gi ca h s hiu chnh F thng ln hn 1. Nu F sai khc 1 qu 1%, ngha l F ln hn 1.01 hoc nh hn 0.99 ta cn phi pha long dung dch hoc lm cho m c thm bng cch da trn cc php tnh sau y: - Trong trng hp phi pha long dung dch (F > 1) ngi ta ly hiu ca F v 1 ri nhn hiu s thu c vi 1000. Kt qu ca tch s tng ng vi s lng nc cn thm vo mi lt dung dch pha long. Nu gp trng hp phi lm c thm (F < 1) ngi ta ly 1 tr i gi tr ca F ri ly hiu nhn vi s lng gam ha cht cn thit pha 1 lt dung dch ng chun yu cu, tch s tm c biu th lng ha cht cn thm vo 1 lt dung dch. - xc nh h s hiu chnh ngi ta phi chun t nht ba ln. Nu kt qu ca nhng ln chun khng lch nhau qu 0.05ml, ly s trung bnh cng ca nhng kt qu thu c. Nu s chnh lch gia cc ln chun cao hn 0.05ml, cn phi tin hnh chun li cho n khi kt qu nh . Mun cho s chun khng sai qu 0.1% cn phi ly cho mi ln chun t nht khong 20 30ml dung dch.

9

Php tnh nhng h s hiu chnh i vi cc dung dch chun thc hin theo nhng phng php sau y: Nu dng ha cht tinh khit xc nh chun, h s hiu chnh tnh theo cng thc:F = a T .V

a l lng ha cht tinh khit, tnh ra gam T l chun l thuyt ca ha cht tinh khit, tnh ra g/l V l th tch ca dung dch pha ch, tnh ra ml. Nu dng dung dch chun c nng bit trc xc nh chun, h s hiu chnh F tnh theo cng thc:F= V0 V

V0 l th tch dung dch chun, tnh ra ml. V l th tch dung dch pha ch, tnh ra ml. Cc dung dch chun thng dng Dung dch HCl 1N (1ml = 0.3646g HCl) Ha 85ml HCl m c (D20 = 1.19) vo nc ct cho va 1000ml. Xc nh h s hiu chnh v hiu chnh dung dch. Pha cc dung dch HCl 0.5N, 0.1Nt dung dch HCl 1N trn bng cch pha long theo t l v xc nh li h s hiu chnh. Dung dch acid oxalic 0.1N (1ml = 0.006303g C2H2O4.2H2O) Ha tan 6.40g acid oxalic vo nc, thm nc ct cho va 1000ml. Bo qun trong l thy tinh nt mi, trnh nh sng. Xc nh h s hiu chnh bng KMnO4 mi trng H2SO4 v hiu chnh dung dch. Dung dch H2SO4 1N (1ml = 0.04904g H2SO4). Rt t t cn thn v va rt va lc u 30ml acid sulfuric m c vo 1020ml nc. Xc nh h s hiu chnh v hiu chnh dung dch.

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Pha cc dung dch H2SO4 0.5N, 0.1Nt dung dch H2SO4 1N trn bng cch pha long theo t l v xc nh li h s hiu chnh. Dung dch KOH 0.5N trong cn (1ml = 0.02805g KOH) Ha 10g KOH nghin nh vo 1000ml cn 95o, un si hn hp vi ng sinh hn hon lu trong 30 pht, sau ct ly cn. Dng cn ny pha dung dch KOH 0.5N nh sau: Ha tan 35g KOH vo 20ml nc trong mt bnh c nt cao su v cho thm cn tinh ch trn va 1000ml. yn 24 gi, ri gn nhanh phn cht lng trong sang mt bnh thy tinh mu v y kn bng nt cao su. Bo qun trnh nh sng. Xc nh chun khi s dng. Dung dch NaOH 1N (1ml = 0.040g NaOH) Ha tan 45g NaOH vo 50ml nc trong mt bnh y kn bng nt cao su. yn 24 gi ri gn ly phn cht lng trong trn v pha long vi nc mi un si ngui cho thnh 1000ml. Bo qun trng l thu tinh, nt cao su kn, trnh kh CO2 trong khng kh. Xc nh h s hiu chnh vi acid oxalic tinh th hoc dung dch chun v hiu chnh dung dch. Pha cc dung dch NaOH 0.5N, 0.1N t dung dch NaOH 1N trn bng cch pha long theo t l v xc nh li h s hiu chnh. Dung dch AgNO3 0.1N (1ml = 0.01690g AgNO3) Ha tan 17.5g AgNO3 vo nc v thm nc va 1000ml. Bo qun trong l thy tinh mu, trnh nh sng. Xc nh h s hiu chun v hiu chun dung dch. Dung dch Iot 0.1N (1ml = 0.01269g I2) Ha tan 13g iot tinh th trong mt dung dch cha 36g KI v 56ml nc, ri pha long vi nc n va 1000ml. Bo qun trong l thy tinh mu, nt mi, trnh nh sng. Xc nh h s hiu chnh vi dung dch chun natri thiosulfat 0.1N, ch th mu h tinh bt v hiu chnh dung dch. Dung dch KMnO4 0.1N (1ml = 0.00316g KMnO4)

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Ha tan khong 3.30g KMnO4 trong 1000ml nc. un si dung dch trong 10 pht. y nt bnh v yn trong hai ngy, ri lc trn phu lc thy tinh xp, bo qun trong l thy tinh mu, nt mi. Xc nh h s hiu chnh: Ly chnh xc bng buret, 25ml dung dch KMnO4 trn, cho vo bnh thy tinh c nt mi cha sn 20ml dung dch KI 10%. Acid ha dung dch vi 2ml H2SO4 long v y kn bng nt mi tm t bng dung dch KI, yn ch ti 10 pht, pha long vi 200ml nc, va dng nc ny ra nt mi. Chun iot c gii phng ra bng dung dch natri thiosulfat 0.1N vi ch th h tinh bt. C th xc nh h s hiu chnh bng phng php sau: cn chnh xc khong 0.20g natri oxalat (phn t lng 134.0) sy kh 110 oC n khi lng khng i. Ha tan trong 80ml H2SO4 long v un nng ti 70oC, chun bng dung dch KMnO4 trn, va nh t t, va lc lin tc, cho n khi c mu hng nht bn vng trong 15 giy. Lc kt thc chun , nhit ca dung dch khng c xung di 60oC. Tnh h s hiu chnh v hiu chnh dung dch Dung dch chun KSCN 0.1N (1ml = 0.009717g KSCN) Ha tan 9.717g KSCN vo nc v thm nc va 1000ml. Xc nh h s hiu chnh vi dung dch chun AgNO3 0.1N mi trng acid nitric, ch th mu l phn st amn. Dung dch chun NH4SCN 0.1N (1ml = 0.007612g NH4SCN) Ha tan 8g NH4SCN vo nc thm nc va 1000ml. Xc nh h s hiu chnh nh vi KSCN v hiu chnh dung dch. Dung dch chun Na2S2O3 0.1N (1ml = 0.02482g Na2S2O3.5H2O) Ha tan 26g natri thiosulfat (cn gi l natri hyposulfit) v 0.1g natri carbonat vo nc mi un si ngui v thm nc va 1000ml. yn 10 ngy, trnh nh sng, nu c ta th gn ly phn dung dch trn, bo qun trnh

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kh CO2 trong khng kh. Xc nh h s hiu chnh vi dung dch chun iot, ch th mu h tinh bt v hiu chnh dung dch. Dung dch chun Complexon III 0.1N (0.05M) (1ml = 0.01861g C10H14O8N2Na2.2H2O) Ha tan 18.80g Complexon III vo nc v thm nc va 1000ml, ri lc. Ghi ch: 1. Nc dng pha dung dch Complexon III cn bo m nhng iu kin sau y: 100ml nc, thm 5ml dung dch m amoniac v vi git dung dch eriocrom en T, mu tm ca dung dch phi chuyn sang mu xanh khi thm 1 2 git dung dch Complexon III 0.05M (0.1N) v mu xanh phi chuyn sang tm khi thm 1 2 git dung dch km 0.1N. Nu nc khng p ng c cc tiu chun trn th cn cho chy qua ct cationit vi tc 1 git trong 1 giy. 2. Nu Complexon III khng phi l loi dng cho phn tch nh lng c th tinh ch nh sau: ha tan 100g Complexon III trong 1000ml nc nng, thm 10g than hot tnh vo dung dch ang nng, khuy mnh trong 10 pht ri lc. Dch lc li un si ri va khuy va thm 46.80ml HCl m c. ngui t t cho kt tinh acid etylen diamin tetracetic (Trilon B), lc ly tinh th to thnh , bng phu thy tinh xp s 2 v ra bng nc lnh cho n khi ht phn ng colorur. Sy kh n khi lng khng i 90 100oC. pha ch dung dch Complex III cn khong 14.60g acid etylen diamin tetracetic v ha tan vo dung dch NaOH 0.1N cho va 1000ml. Xc nh h s hiu chnh: ha tan khong 3.27g km kim loi vo 40ml dung dch H2SO4 long (1/5) trong mt bnh nh mc 1000ml v thm nc n vch. Ly chnh xc 25ml dung dch km trn cho thm 5ml dung dch amoniac, khong 0.1g ch th mu Eriocrom en T, 20ml nc, lc cho tan. Chun bng dung dch Complexon III pha ch trn cho n khi mu chuyn t tm sang ti. H s hiu chnh:13

F =

25 .a 1000 .0,003269 .V

Ch : Trilon B (cn gi l Complexon II) l acid etylen diamin tetracetic, hin nay c gi l EDTA (ch u ca tn gi ha hc). Complex III l mui dinatri ca acid etylen diamin tetracetic. V cng dng ca hai cht ny ging ht nhau nn ngi ta thng gi ln ln, coi nh Trilon B l Complexon III. Khi dng, cn ch xem cng thc ha hc ghi trn nhn l ha cht trnh nhm khi tnh ton phn t gam, ng lng gam pha dung dch chun. Bng cc khong pH v vng chuyn mu ca cc cht ch th mu Tn Metyl tm Thymol xanh Tropeolin 00 Metyl tm Dimetyl vng Metyl da cam Bromophenol xanh Congo Bromocrezol lc Alizarin Metyl Lacmoit Bromocrezol ta Bromothymol xanh trung tnh Phenol Crezol Dung mi Nc Nc + kim Cn metylic Nc + kim Nc Cn 90o Nc Cn + nc Cn + nc Cn 20o Nc Cn 90o Cn 90o Cn + nc Cn 20o Nc Acid acetic Nc + kim Nc + kim Nng % 0.1 0.05 0.3 0.1 0.1 0.1 0.1 0.1 0.1 0.02 0.1 0.1 v 0.2 0.1 0.1 0.1 0.1 0.1 0.04 0.04 khong pH chuyn mu 0.1 - 1.5 1.2 - 2.8 1.3 - 3.2 1.5 - 3.2 2.9 - 4.0 3.0 - 4.4 3.0 - 4.6 3.0 - 5.2 3.8 - 5.4 3.7 - 5.2 4.2 - 6.3 4.0 - 6.4 5.2 - 6.8 6.0 - 7.6 6.8 - 8.0 6.8 - 8.4 7.2 - 8.8 Vng chuyn mu Vng - lc - vng - vng Lc - tm da cam - vng - vng Vng - xanh tm Xanh - tm - Vng - xanh Vng - tm - vng - xanh Vng nht - tm ta Vng - xanh - vng Vng - Vng - nu

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Naphtolphtalein Phenolphtalein Thymolphtalein

Cn 50o Cn 90o Cn 90o

0.1 1 0.1

7.3 - 8.7

8.2 - 10.0 9.3 - 10.5 10.1 Alizarin vng Nc 0.1 12.1 11.5 Da cam G Nc 0.1 14.0 Phn t gam ca axit etylen diamin tetracetic l 292. Nguyn tc chung s dng ch th mu:

Hng nht - xanh lc Khng mu - Khng mu - xanh Vng - tm hng Vng - tm hng

Phn t gam ca mui dinatri ca n, kt tinh vi 2 phn t nc l 372.-

Trung ha cc baz yu bng acid mnh, dng ch th mu chuyn mu Trung ha cc acid yu bng baz mnh, dng ch th mu chuyn mu Trung ha cc acid mnh bng cc baz mnh, dng ch th mu chuyn

trong vng pH < 7.-

trong vng pH > 7-

mu trong vng pH t 4 n 10.

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