Nrog ntau yam ntawm cov khoom siv organic, muaj cov sib xyaw tshwj xeeb uas muaj cov xim hloov pauv hauv ib puag ncig sib txawv. Ua ntej lub advent ntawm niaj hnub hluav taws xob pH meters, cov ntsuas yog indispensable "cov cuab yeej" rau kev txiav txim siab acid-base indicators, As, thiab tseem yuav siv nyob rau hauv lub chaw soj nstuam xyaum ua auxiliary tshuaj nyob rau hauv analytical chemistry, thiab nyob rau hauv tsis muaj cov khoom tsim nyog..
ntsuas ntsuas yog dab tsi?
Thawj chiv keeb, cov cuab yeej ntawm cov tebchaw no hloov xim hauv ntau yam xov xwm tau siv dav los txiav txim siab cov kua qaub-puag cov khoom hauv cov tshuaj, uas pab txiav txim siab tsis yog qhov nruab nrab ntawm qhov nruab nrab, tab sis kuj tseem kos duab. kev txiav txim siab txog cov khoom siv tshuaj tiv thaiv tshwm sim. Qhov taw qhia cov kev daws teeb meem txuas ntxiv siv rau hauv kev xyaum ua haujlwm los txiav txim siab qhov concentration ntawm cov tshuaj los ntawm titration thiab tso cai rau koj kawm paub siv cov txheej txheem improvised rau qhov tsis muaj.niaj hnub pH meters.
Muaj ntau ntau ntau yam tshuaj, txhua yam uas nkag siab zoo rau thaj chaw nqaim: feem ntau nws tsis tshaj 3 cov ntsiab lus ntawm cov ntaub ntawv teev. Ua tsaug rau ntau yam chromophores thiab lawv cov kev ua haujlwm qis ntawm lawv tus kheej, cov kws tshawb fawb tau tswj hwm los tsim cov ntsuas thoob ntiaj teb uas tau siv dav hauv kev sim thiab kev tsim khoom.
siv ntau pH ntsuas
Nws yog ib qho tseem ceeb uas ntxiv rau cov khoom ntiag tug, cov khoom sib txuas no muaj peev xwm dyeing zoo, uas tso cai rau lawv siv rau dyeing fabrics hauv kev lag luam textile. Ntawm ntau cov xim ntsuas hauv chemistry, cov npe nrov tshaj plaws thiab siv tau yog methyl txiv kab ntxwv (methyl txiv kab ntxwv) thiab phenolphthalein. Feem ntau lwm cov chromophores tam sim no siv sib xyaw ua ke, lossis rau cov khoom sib xyaw thiab cov tshuaj tiv thaiv.
Methyl txiv kab ntxwv
Ntau cov xim muaj npe rau lawv cov xim xim hauv qhov chaw nruab nrab, uas kuj muaj tseeb rau cov chromophore no. Methyl txiv kab ntxwv yog azo dye muaj ib pab pawg - N=N - nyob rau hauv nws muaj pes tsawg leeg, uas yog lub luag hauj lwm rau kev hloov ntawm cov xim ntawm qhov taw qhia mus rau liab nyob rau hauv ib tug acidic ib puag ncig, thiab mus rau daj nyob rau hauv ib tug alkaline ib tug. Azo tebchaw lawv tus kheej tsis yog lub hauv paus muaj zog, txawm li cas los xij, muaj cov pab pawg neeg pub dawb (‒ OH, - NH2, ‒ NH (CH3), ‒ N (CH 3) 2 thiab lwm yam) nce qhov pib ntawm ib qho ntawm cov nitrogen atoms,uas dhau los ua muaj peev xwm txuas cov hydrogen protons raws li tus neeg txais nyiaj pub dawb. Yog li ntawd, thaum hloov cov concentrations ntawm H+ ions nyob rau hauv cov tshuaj, ib tug kev hloov nyob rau hauv cov xim ntawm lub acid-base qhia tau pom.
Ntau ntawm kev ua methyl txiv kab ntxwv
Tau txais methyl txiv kab ntxwv los ntawm cov tshuaj tiv thaiv nrog diazotization ntawm sulfanilic acid C6H4(SO3H)NH2 ua ke nrog dimethylaniline C6H5N(CH3)2. Sulfanilic acid yog yaj hauv cov tshuaj sodium alkali los ntawm kev ntxiv sodium nitrite NaNO 2, thiab tom qab ntawd txias nrog dej khov kom ua tiav cov kev sib txuas ntawm qhov kub thiab txias kom ze li ntawm 0 ° C thiab hydrochloric acid HCl ntxiv. Tom ntej no, ib qho kev sib cais ntawm dimethylaniline hauv HCl yog npaj, uas yog poured rau hauv thawj cov tshuaj thaum txias, tau ib tug dye. Nws yog ntxiv alkalized, thiab tsaus txiv kab ntxwv crystals precipitate los ntawm cov tshuaj, uas, tom qab ob peb teev, lim tawm thiab qhuav nyob rau hauv ib da dej.
YPhenolphthalein
Cov chromophore no tau txais nws lub npe los ntawm kev ntxiv cov npe ntawm ob lub reagents koom nrog hauv nws cov synthesis. Cov xim ntawm qhov taw qhia yog qhov tseem ceeb rau nws cov kev hloov ntawm cov xim nyob rau hauv ib qho alkaline nruab nrab nrog kev nrhiav tau ntawm raspberry (liab-violet, raspberry-liab) hue, uas yuav tsis muaj xim thaum cov tshuaj muaj zog alkalized. Phenolphthalein tuaj yeem siv ntau hom nyob ntawm qhov pH ntawm ib puag ncig, thiab nyob rau hauv cov acidic ib puag ncig nws muaj xim txiv kab ntxwv.
Chromophore no yog tsim los ntawm condensation ntawm phenol thiab phthalic anhydride nyob rau hauv lub xub ntiag ntawm zinc chloride ZnCl2 los yog concentrated sulfuric acid H 2 SO 4. Hauv lub xeev cov khoom, phenolphthalein molecules yog cov xim tsis muaj kob.
Yav dhau los, phenolphthalein tau nquag siv hauv kev tsim cov tshuaj laxatives, tab sis maj mam nws siv tau txo qis vim yog cov khoom tsim tau.
Litmus
Qhov ntsuas no yog ib qho ntawm thawj cov tshuaj siv los ntawm cov khoom siv xov xwm. Litmus yog ib qho kev sib xyaw ntawm ntuj sib xyaw uas tau los ntawm qee hom lichens. Nws yog siv tsis tau tsuas yog raws li ib tug coloring neeg sawv cev, tab sis kuj raws li ib tug txhais tau tias los txiav txim lub pH ntawm nruab nrab. Qhov no yog ib qho ntawm thawj qhov ntsuas uas tau pib siv los ntawm tus txiv neej hauv kev siv tshuaj lom neeg: nws yog siv rau hauv daim ntawv ntawm cov tshuaj aqueous los yog strips ntawm cov ntawv lim impregnated nrog nws. Litmus nyob rau hauv lub xeev muaj zog yog cov hmoov tsaus nrog ib tug me ntsis ammonia tsw. Thaum yaj hauv dej ntshiab, cov xim ntawm qhov taw qhia ua ntshav, thiab thaum acidified, nws tig liab. Nyob rau hauv ib qho alkaline nruab nrab, litmus hloov xiav, uas ua rau nws muaj peev xwm siv nws raws li ib tug universal qhia rau kev txiav txim ntawm qhov nruab nrab qhov taw qhia.
Nws tsis tuaj yeem tsim kom raug lub tshuab thiab qhov xwm txheej ntawm cov tshuaj tiv thaiv uas tshwm sim thaum pH hloov hauv cov qauv ntawm litmus Cheebtsam, txij li nws tuaj yeem suav txog 15 qhov sib txawv, qee qhov. Tej zaum lawv yuav yog cov khoom xyaw uas tsis muaj zog, uas ua rau lawv cov kev tshawb fawb ntawm cov tshuaj thiab lub cev muaj zog.
Universal indicator paper
Nrog rau kev txhim kho ntawm kev tshawb fawb thiab kev tshwm sim ntawm cov ntaub ntawv qhia, kev tsim cov kev ntsuas ib puag ncig tau yooj yim dua, txij li tam sim no nws tsis tsim nyog kom muaj cov kua reagents npaj rau txhua qhov kev tshawb fawb, uas cov kws tshawb fawb thiab cov kws tshawb fawb forensic. tseem ntse siv. Yog li, cov kev daws teeb meem tau hloov los ntawm cov ntaub ntawv qhia thoob ntiaj teb, uas, vim lawv qhov dav ntawm qhov kev txiav txim, yuav luag tag nrho cov kev xav tau siv lwm cov ntsuas acid-base.
Cov khoom xyaw ntawm cov impregnated strips yuav txawv ntawm cov chaw tsim khoom rau cov chaw tsim khoom, yog li cov npe kwv yees ntawm cov khoom xyaw yuav muaj raws li hauv qab no:
- phenolphthalein (0-3, 0 thiab 8, 2-11);
- (di)methyl yellow (2, 9–4, 0);
- methyl txiv kab ntxwv (3, 1–4, 4);
- methyl liab (4, 2–6, 2);
- bromothymol xiav (6, 0–7, 8);
- α‒naphtholphthalein (7, 3–8, 7);
- thymol xiav (8, 0–9, 6);
- cresolphthalein (8, 2–9, 8).
Lub ntim yuav tsum muaj cov qauv xim xim uas tso cai rau koj los txiav txim siab pH ntawm qhov nruab nrab ntawm 0 txog 12 (kwv yees 14) nrog qhov tseeb ntawm ib tus lej.
Ntawm lwm yam, cov tshuaj no tuaj yeem siv ua ke hauv cov dej thiab dej cawv, uas ua rau kev siv cov khoom sib xyaw no yooj yim heev. Txawm li cas los xij, qee yam ntawm cov khoom no yuav tsis zoo soluble hauv dej, yog li nws tsim nyogxaiv universal organic solvent.
Vim lawv cov khoom, cov ntsuas acid-puag tau pom lawv daim ntawv thov hauv ntau qhov kev tshawb fawb, thiab lawv cov kev sib txawv tau ua rau nws muaj peev xwm tsim cov universal sib tov uas nkag siab rau ntau yam pH ntsuas.
