Nitrite ion yog ib qho ion uas muaj ib lub nitrogen atom thiab ob lub atoms oxygen. Cov nitrogen hauv cov ion no muaj tus nqi ntawm +3, yog li tus nqi ntawm tag nrho cov ion yog -1. Lub particle yog univalent. Cov mis ntawm nitrite ion yog TSIS MUAJ 2 -. Lub anion muaj ib tug nonlinear configuration. Cov tshuaj uas muaj cov khoom no hu ua nitrites, piv txwv li sodium nitrite - NaNO2, nyiaj nitrite - AgNO2..
Lub cev thiab tshuaj lom neeg
Alkali, alkaline ntiaj teb thiab ammonium nitrites tsis muaj xim lossis xim daj me ntsis crystalline. Potassium, sodium, barium nitrites yaj zoo hauv dej, nyiaj, mercury, tooj liab nitrites - tsis zoo. Raws li qhov kub thiab txias, cov solubility nce. Yuav luag tag nrho cov nitrites tsis zoo soluble nyob rau hauv ethers, alcohols thiab low-polarity solvents.
Table. Lub cev yam ntxwv ntawm qee cov nitrites.
| yam ntxwv | Ntiaj teb nitrite | YBarium nitrite | ||
|
Tpl,° |
440 |
120 (decomposed) |
220 (decomposed) |
277 |
|
∆H0rev, kJ/mol |
- 380, 0 | - 40, 0 | -766, 0 | - 785, 5 |
| S0298, J/(molK) | 117, 2 | 128, 0 | 175, 0 | 183, 0 |
| Kev daws hauv dej, g hauv 100 g |
306, 7 (200C) |
0, 41 (250C) |
84, 5 (180C) |
67, 5 (200C) |
Nitrites tsis tiv taus cua sov: tsuas yog alkali hlau nitrites yaj yam tsis muaj decomposition. Raws li qhov tshwm sim ntawm decomposition, gaseous khoom raug tso tawm - O2 , TSIS, N2, NO2, thiab cov khoom siv - hlau oxide lossis hlau nws tus kheej. Piv txwv li, qhov decomposition ntawm nyiaj nitrite (twb ntawm 40 ° C) yog nrog los ntawm kev tso tawm ntawm cov nyiaj thiab nitrogen oxide (II):
2AgNO2=AgNO3 + Ag + NO↑
Vim tias qhov decomposition tau mus nrog kev tso tawm ntawm cov pa roj ntau, cov tshuaj tiv thaiv tuaj yeem tawg, piv txwv li, nyob rau hauv cov ntaub ntawv ntawm ammonium nitrite.
Redox khoom
Cov nitrogen atom hauv nitrite ion muaj tus nqi nruab nrab ntawm +3, uas yog vim li cas nitrites yog tus cwj pwm los ntawm ob qho tib si oxidizing thiab txo cov khoom. Piv txwv li, nitrites yuav decolorize ib tug daws ntawm poov tshuaj permanganate nyob rau hauv ib tug acidic ib puag ncig, uas qhia cov khoomoxidizer:
5KNO2 + 2KMnO4 +3H2SO4 =3H2O + 5KNO3 + 2MnSO4 + K 2SO4
Nitrite ions nthuav tawm cov khoom ntawm tus neeg sawv cev txo qis, piv txwv li, hauv cov tshuaj tiv thaiv nrog cov tshuaj muaj zog ntawm hydrogen peroxide:
NO2- + H2O2=NO3- + H2O
Tus neeg sawv cev txo qis yog nitrite thaum cuam tshuam nrog nyiaj bromate (acidified tov). Cov tshuaj tiv thaiv no yog siv rau hauv tshuaj ntsuam xyuas:
2NO2- + Ag+ + BrO2 -=2NO3- + AgBr↓
Ib qho piv txwv ntawm kev txo cov khoom yog qhov muaj txiaj ntsig zoo rau nitrite ion - kev sib cuam tshuam ntawm cov xim tsis muaj xim [Fe(H2O) 6] 2+ nrog acidified sodium nitrite tov nrog xim av.
Theoretical foundations of NO2 detection¯
Nitrous acid, thaum rhuab, disproportionates rau nitric oxide (II) thiab nitric acid:
HNO2 + 2HNO2=NO3- + H2O + 2NO↑ + H+
Yog li ntawd, nitrous acid tsis tuaj yeem sib cais los ntawm nitric acid los ntawm boiling. Raws li tuaj yeem pom los ntawm qhov sib npaug, nitrous acid, decomposing, ib nrab hloov mus rau nitric acid, uas yuav ua rau muaj kev ua yuam kev hauv kev txiav txim siab cov ntsiab lus ntawm nitrates.
Yuav luag tag nrho cov nitrites yaj hauv dej, qhov tsawg tshaj plaws soluble ntawm cov tebchaw yog nyiaj nitrite.
Nitrite ion nws tus kheejnws yog xim tsis muaj xim, yog li nws tau kuaj pom los ntawm kev cuam tshuam ntawm kev tsim ntawm lwm cov xim sib xyaw. Cov nitrites ntawm uncolored cations kuj tsis muaj xim.
Cov tshuaj tiv thaiv zoo
Muaj ntau txoj hauv kev zoo los txiav txim siab nitrite ions.
1. Reaction forming K3[Co(NO2)6].
Nyob rau hauv ib lub raj tshuaj muab 5 tee ntawm cov tshuaj uas muaj nitrite, 3 tee ntawm cob alt nitrate tov, 2 tee ntawm acetic acid (diluted), 3 tee ntawm poov tshuaj chloride tov. Hexanitrocob altate (III) K3[Co(NO2)6] yog tsim - daj crystalline nag xob nag cua. Cov nitrate ion hauv cov tshuaj ntsuam xyuas tsis cuam tshuam nrog kev tshawb pom ntawm nitrites.
2. Iodide oxidation tshuaj tiv thaiv.
Nitrite ions oxidize iodide ions nyob rau hauv ib puag ncig acidic.
2HNO2 + 2I- + 2H+ =2NO↑ + I 2↓ + 2H2O
Nyob rau hauv chav kawm ntawm cov tshuaj tiv thaiv, lub ntsiab iodine yog tsim, uas yog yooj yim pom los ntawm starch staining. Ua li no, cov tshuaj tiv thaiv tuaj yeem nqa tawm ntawm daim ntawv lim yav dhau los impregnated nrog cov hmoov txhuv nplej siab. Cov lus teb yog rhiab heev. Cov xim xiav tshwm txawm tias muaj cov kab mob nitrites: qhov qhib qhov tsawg kawg nkaus yog 0.005 mcg.
Cov ntawv lim yog impregnated nrog cov hmoov txhuv nplej siab, 1 tee ntawm 2N tov ntawm acetic acid, 1 tee ntawm kev sim tshuaj, 1 poob ntawm 0.1N tov ntawm poov tshuaj iodide ntxiv rau nws. Nyob rau hauv lub xub ntiag ntawm nitrite, lub nplhaib xiav los yog qhov chaw tshwm. Kev kuaj pom yog cuam tshuam los ntawm lwm cov oxidants ua rau tsim iodine.
3. Cov tshuaj tiv thaiv nrog poov tshuaj permanganatepoov tshuaj.
Muab 3 tee ntawm poov tshuaj permanganate tov, 2 tee ntawm sulfuric acid (diluted) nyob rau hauv ib lub raj kuaj. Cov sib tov yuav tsum tau rhuab mus rau 50-60 ° C. Ua tib zoo ntxiv ob peb tee ntawm sodium los yog potassium nitrite. Cov tshuaj permanganate yuav tsis muaj xim. Lwm cov tshuaj txo qis tam sim no nyob rau hauv cov tshuaj ntsuam xyuas, muaj peev xwm ntawm oxidizing cov permanganate ion, yuav cuam tshuam nrog kev tshawb nrhiav NO2-..
4. Cov tshuaj tiv thaiv nrog hlau sulfate (II).
Ferrous sulfate txo nitrite rau nitrate hauv ib puag ncig acidic (dilute sulfuric acid):
2KNO2 (TV) + 2H2SO4 (diff.) + 2FeSO4 (solid)=2NO↑ + K2SO4 + Fe2(SO4)3 + 2H2O
Qhov tshwm sim nitric oxide (II) cov ntaub ntawv nrog ntau tshaj Fe2+ (uas tseem tsis tau hnov qab) xim av complex ions:
NO + Fe2+=[FeNO]2+
NO + FeSO4=[FeNO]SO4
Nws yuav tsum tau sau tseg tias nitrites yuav hnov mob nrog dilute sulfuric acid, thiab nitrates yuav hnov mob nrog concentrated sulfuric acid. Yog li ntawd, nws yog dilute acid uas yuav tsum tau mus ntes cov nitrite ion.
5. Cov tshuaj tiv thaiv antipyrine.
NO2- nrog antipyrine hauv cov kua qaub nruab nrab muab cov tshuaj ntsuab.
6. Cov tshuaj tiv thaiv nrog rivanol.
NO2-- nrog rivanol lossis ethacridine (I) hauv cov kua qaub nruab nrab muab cov tshuaj liab.
Kev txiav txim siab ntawm cov ntsiab lus nitrite hauv dej
Raws li GOSTCov ntsiab lus ntau ntawm nitrite ions hauv dej yog txiav txim siab los ntawm ob txoj hauv kev photometric: siv sulfanilic acid thiab siv 4-aminobenzenesulfonamide. Thawj qhov yog arbitrage.
Vim yog qhov tsis ruaj khov ntawm nitrites, lawv yuav tsum txiav txim siab tam sim tom qab kuaj, lossis cov qauv tuaj yeem khaws cia los ntawm kev ntxiv 1 ml ntawm sulfuric acid (concentrated) los yog 2-4 ml ntawm chloroform rau 1 liter dej; koj tuaj yeem txias cov qauv mus rau 4 ° C.
Turbid lossis xim dej yog ntxuav nrog txhuas hydroxide los ntawm kev ntxiv 2-3 ml ntawm kev ncua rau 250-300 ml dej. Qhov sib tov yog shaken, ib txheej pob tshab yog coj los soj ntsuam tom qab kev qhia meej.
Kev txiav txim siab ntawm nitrite cov ntsiab lus nrog sulfanilic acid
Lub ntsiab lus ntawm txoj kev: nitrites ntawm cov qauv tshuaj ntsuam cuam tshuam nrog sulfanilic acid, cov ntsev tshwm sim nrog 1-naphthylamine nrog kev tso tawm cov xim liab-violet azo dye, nws cov nyiaj txiav txim siab photometrically, tom qab ntawd cov concentration ntawm nitrites nyob rau hauv cov qauv dej yog xam. 1-naphthylamine thiab sulfanilic acid thiab yog ib feem ntawm Griess reagent.
Kev txiav txim siab ntawm nitrite ions: txheej txheem
Rau 50 ml ntawm cov qauv dej, ntxiv 2 ml ntawm kev daws Griess reagent hauv acetic acid. Sib tov thiab incubate rau 40 feeb ntawm qhov kub thiab txias los yog 10 feeb ntawm 50-60 ° C hauv dej da dej. Tom qab ntawd lub optical ceev ntawm qhov sib tov yog ntsuas. Raws li cov qauv dawb paug, cov dej distilled yog siv, uas yog npaj zoo ib yam li cov qauv ntawm cov dej tshuaj ntsuam xyuas. Qhov concentration ntawm nitrites yog xam los ntawm cov mis:
X=K∙A∙50∙f / V, qhov twg: K yog tus coefficientcalibration yam ntxwv, A yog tus nqi ntawm qhov muag qhov ntom ntom ntawm cov qauv ntsuas dej tshem tawm cov nqi ntawm qhov muag qhov ntom ntom ntawm cov qauv dawb, 50 - ntim ntim ntim ntim, f – dilution factor (yog tias tus qauv tsis diluted, f=1), V yog qhov ntim ntawm aliquot coj los tshuaj xyuas.
Nitrites hauv dej
nitrite ions tuaj ntawm qhov twg hauv cov dej khib nyiab? Nitrites yeej ib txwm muaj nyob rau hauv me me hauv dej nag, saum npoo thiab dej hauv av. Nitrites yog ib theem nruab nrab ntawm kev hloov pauv ntawm nitrogen-muaj tshuaj uas ua los ntawm cov kab mob. Cov ions no yog tsim thaum lub sij hawm oxidation ntawm ammonium cation rau nitrates (nyob rau hauv lub xub ntiag ntawm oxygen) thiab nyob rau hauv lub opposite tshuaj - txo cov nitrates rau ammonia los yog nitrogen (nyob rau hauv tsis muaj oxygen). Tag nrho cov tshuaj tiv thaiv no yog ua los ntawm cov kab mob, thiab cov organic teeb meem yog lub hauv paus ntawm nitrogen-muaj tshuaj. Yog li ntawd, cov ntsiab lus ntau ntawm nitrites hauv dej yog qhov qhia txog kev huv huv. Tshaj li cov qauv ntawm cov ntsiab lus nitrite qhia tias muaj kuab paug ntawm dej. Kev nkag mus ntawm cov dej ntws los ntawm cov tsiaj txhu ua liaj ua teb, cov chaw tsim khoom, cov chaw lag luam, kev ua qias tuaj hauv dej nrog dej los ntawm thaj chaw uas siv cov chiv nitrogen yog cov laj thawj tseem ceeb rau cov ntsiab lus siab ntawm nitrites hauv dej.
Tau txais
Hauv kev lag luam, sodium nitrite tau txais los ntawm kev nqus cov pa roj nitrous (ib qho sib xyaw ntawm TSIS TAU thiab TSIS MUAJ 2) nrog NaOH lossis Na 2 CO daws 3 ua raws li sodium nitrite crystallization:
NO +NO2 + 2NaOH (cold)=2NaNO2 + H2O
Cov tshuaj tiv thaiv nyob rau hauv lub xub ntiag ntawm oxygen pib nrog kev tsim ntawm sodium nitrate, yog li anoxic mob yuav tsum tau muab.
Potassium nitrite yog tsim los ntawm tib txoj kev hauv kev lag luam. Tsis tas li ntawd, sodium thiab potassium nitrite tuaj yeem tau txais los ntawm oxidizing lead nrog nitrate:
KNO3 (conc) + Pb (sponge) + H2O=KNO2+ Pb(OH)2↓
KNO3 + Pb=KNO2 + PbO
Cov tshuaj tiv thaiv zaum kawg tshwm sim ntawm qhov kub ntawm 350-400 ° C.
