在酸碱滴定法中,通常通过观察酸碱指示剂颜色的突然变化来确定滴定终点。这类指示剂多为有机弱酸或有机弱碱。在碱性溶液中,它们会失去质子由酸式转化为碱式(以In-表示);而在酸性溶液中,则会得到质子由碱式转化为酸式(以HIn表示)。这一过程伴随着结构和颜色的变化。
由于不同指示剂的解离平衡常数KHlπ各不相同,它们的变色范围也有所不同。有的在酸性环境中变色,有的则在中性和弱碱性条件下变化,还有一些仅在强碱性溶液中显示颜色。因此,在选择酸碱指示剂时,可以根据滴定等当点附近的pH值和突跃大小来做出合适的选择。
例如,在使用强碱滴定弱酸的过程中,等当点附近通常呈现弱碱性环境,此时选用酚酞或百里酚蓝作为指示剂较为适宜;而甲基橙因其在酸性溶液中变色的特点,则不适用于此情况。相反,若进行强酸滴定弱碱的操作,在等当点附近的pH值约为微酸性时,选择甲基红、甲基橙和溴甲酚绿这些能够在酸性环境中变色的指示剂将更为恰当。
中文名称 | 英文名称 | CAS号 | 化学式 | 结构式图片 |
---|---|---|---|---|
龙胆紫 | crystal violet | 548-62-9 | C25H30N3*Cl |
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阿脲四水合物 | Alloxan tetrahydrate | 6010-91-9 | C4H10N2O8 |
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间苯二酚蓝 | Azane;7-hydroxyphenoxazin-3-one | 42249-61-6 | C12H10N2O3 |
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间甲酚紫钠盐 | 3,3-Bis(4-hydroxy-2-methylphenyl)-3H-benzo[d][1,2]oxathiole 2,2-dioxide, sodium salt | 62625-31-4 | C21H18NaO5S |
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间甲酚紫 | m-cresol purple | 2303-01-7 | C21H18O5S |
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锌试剂 | 2-(-2-((-(2-Hydroxy-5-sulfophenyl)diazenyl)-(phenyl)methylene)hydrazinyl)benzoic acid | 135-52-4 | C20H16N4O6S |
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邻菲罗啉 | 1,10-phenanthroline hydrate | 5144-89-8 | C12H8N2*H2O |
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邻甲酚酞 | o-cresolphthalein | 596-27-0 | C22H18O4 |
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荧光兰 | lacmoid | 33869-21-5 | C24H16N2O6 |
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茜素络合指示剂 | alizarin complexone | 3952-78-1 | C19H15NO8 |
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硝苯酚 | 2-hydroxynitrobenzene | 88-75-5 | C6H5NO3 |
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百里酚酞-2',2''-双(甲基亚氨基二乙酸钠盐) | Glycine, N,N'-((3-oxo-1(3H)-isobenzofuranylidene)bis((6-hydroxy-2-methyl-5-(1-methylethyl)-3,1-phenylene)methylene))bis(N-(carboxymethyl)-, tetrasodium salt | 62698-55-9 | C38H40N2Na4O12 |
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百里酚酞 | thymolphthalein | 125-20-2 | C28H30O4 |
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甲基红 | methyl red | 493-52-7 | C15H15N3O2 |
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玫红酸 | aurin | 603-45-2 | C19H14O3 |
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溴甲酚紫 | Bromocresol Purple sodium salt ACS grade | 62625-30-3 | C21H16Br2NaO5S |
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氯酚红 | Chlorophenol red | 4430-20-0 | C19H12Cl2O5S |
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射光蓝浆AG-R | Benzenesulfonic acid, [[4-[[4-(phenylamino)phenyl][4-(phenylimino)-2,5-cyclohexadien-1-ylidene]methyl]phenyl]amino]- | 1186514-33-9 | C37H29N3O3S |
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媒介橙 1 | alizarin yellow R | 2243-76-7 | C13H9N3O5 |
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姜黄素 | curcumin | 458-37-7 | C21H20O6 |
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四溴酚蓝 | tetrabromophenol blue | 4430-25-5 | C19H6Br8O5S |
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吡啶-(2-偶氮-4)间苯二酚 | 4-(2-pyridylazo)resorcinol | 1141-59-9 | C11H9N3O2 |
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双(2,4-二硝基苯)乙酸乙酯 | ethyl bis(2,4-dinitrophenyl)acetate | 5833-18-1 | C16H12N4O10 |
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偶氮胂Ⅲ | arsenazo III | 1668-00-4 | C22H18As2N4O14S2 |
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五甲氧红 | 2.4.2'.4'.2''-Pentamethoxy-triphenylcarbinol | 1755-51-7 | C24H26O6 |
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α-萘黄酮 | α-naphtoflavone | 604-59-1 | C19H12O2 |
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alpha-纳富妥苯 | (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon | 145-50-6 | C27H18O2 |
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N,N'-二苯基联苯二胺 | N,N'-diphenyl-p-phenylenediamine | 531-91-9 | C24H20N2 |
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4,5-二羟基-3,6-双[(2-磺基苯基)偶氮]-2,7-萘二磺酸 | 3,6-Bis(o-sulphophenylazo)-4,5-dihydroxynaphthalene-2,7-disulphonic acid | 1738-02-9 | C22H16N4O14S4 |
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3,8-二溴菲罗啉 | 3,8-dibromo-1,10-phenathroline | 100125-12-0 | C12H6Br2N2 |
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3,3,5,5-四溴酚酞乙酯钾盐 | 3',3'',5',5''-Tetrabromophenolphthalein ethyl ester potassium salt, indicator grade | 62637-91-6 | C22H14Br4KO4 |
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2-硝基苯胺 | 2-nitro-aniline | 88-74-4 | C6H6N2O2 |
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2,9-二溴-1,10-菲罗啉 | 2,9-dibromo-1,10-phenanthroline | 39069-02-8 | C12H6Br2N2 |
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2,5-二巯基噻二唑 | 2,5-Dimercapto-1,3,4-thiadiazole | 1072-71-5 | C2H2N2S3 |
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2,2'-联吡啶 | [2,2]bipyridinyl | 366-18-7 | C10H8N2 |
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1-萘酚酞 | α-naphtholphthalein | 596-01-0 | C28H18O4 |
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1,3,5-三硝基苯 | TNB | 99-35-4 | C6H3N3O6 |
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1,10-菲罗啉 | 1,10-Phenanthroline | 66-71-7 | C12H8N2 |
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—— | 1(3H)-Isobenzofuranone, 3,3-bis(4-hydroxyphenyl)-, disodium salt | 518-51-4 | C20H12Na2O4 |
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—— | Benzoic acid, 2-[[[(2-hydroxy-5-sulfophenyl)azo]phenylmethylene]hydrazino]- | 62625-22-3 | C20H16N4O6S |
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—— | (2,4-Diaminophenyl)-(4-ethoxyphenyl)iminoazanium;chloride | 2313-87-3 | C14H17ClN4O |
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—— | 1(4H)-Naphthalenone, 4-[(4-hydroxy-1-naphthalenyl)phenylmethylene]- | 145-50-6 | C27H18O2 |
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—— | p-Naphtholbenzein | 145-50-6 | C27H18O2 |
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—— | 4-(2-pyridylazo)resorcinol | 1141-59-9 | C11H9N3O2 |
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—— | 518-51-4 | C20H14NaO4 |
|
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—— | 2,4,6(1H,3H,5H)-Pyrimidinetrione, 5,5-dihydroxy-, trihydrate | 5629-46-9 | C4H10N2O8 |
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—— | alizarin yellow GG | 584-42-9 | C13H8N3O5*Na |
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—— | methyl red | 845-10-3 | C15H14N3O2*Na |
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—— | m-Cresol purple (sodium) | 62625-31-4 | C21H17NaO5S |
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—— | 2-Carboxy-2-hydroxy-5-sulfoformazylbenzene sodium salt | 135-52-4 | C20H16N4O6S |
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