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酸碱指示剂

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
龙胆紫
阿脲四水合物 Alloxan tetrahydrate 6010-91-9 C4H10N2O8
阿脲四水合物
间苯二酚蓝 Azane;7-hydroxyphenoxazin-3-one 42249-61-6 C12H10N2O3
间苯二酚蓝
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
间甲酚紫钠盐
间甲酚紫 m-cresol purple 2303-01-7 C21H18O5S
间甲酚紫
锌试剂 2-(-2-((-(2-Hydroxy-5-sulfophenyl)diazenyl)-(phenyl)methylene)hydrazinyl)benzoic acid 135-52-4 C20H16N4O6S
锌试剂
邻菲罗啉 1,10-phenanthroline hydrate 5144-89-8 C12H8N2*H2O
邻菲罗啉
邻甲酚酞 o-cresolphthalein 596-27-0 C22H18O4
邻甲酚酞
荧光兰 lacmoid 33869-21-5 C24H16N2O6
荧光兰
茜素络合指示剂 alizarin complexone 3952-78-1 C19H15NO8
茜素络合指示剂
硝苯酚 2-hydroxynitrobenzene 88-75-5 C6H5NO3
硝苯酚
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
百里酚酞-2',2''-双(甲基亚氨基二乙酸钠盐)
百里酚酞 thymolphthalein 125-20-2 C28H30O4
百里酚酞
甲基红 methyl red 493-52-7 C15H15N3O2
甲基红
玫红酸 aurin 603-45-2 C19H14O3
玫红酸
溴甲酚紫 Bromocresol Purple sodium salt ACS grade 62625-30-3 C21H16Br2NaO5S
溴甲酚紫
氯酚红 Chlorophenol red 4430-20-0 C19H12Cl2O5S
氯酚红
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
射光蓝浆AG-R
媒介橙 1 alizarin yellow R 2243-76-7 C13H9N3O5
媒介橙 1
姜黄素 curcumin 458-37-7 C21H20O6
姜黄素
四溴酚蓝 tetrabromophenol blue 4430-25-5 C19H6Br8O5S
四溴酚蓝
吡啶-(2-偶氮-4)间苯二酚 4-(2-pyridylazo)resorcinol 1141-59-9 C11H9N3O2
吡啶-(2-偶氮-4)间苯二酚
双(2,4-二硝基苯)乙酸乙酯 ethyl bis(2,4-dinitrophenyl)acetate 5833-18-1 C16H12N4O10
双(2,4-二硝基苯)乙酸乙酯
偶氮胂Ⅲ arsenazo III 1668-00-4 C22H18As2N4O14S2
偶氮胂Ⅲ
五甲氧红 2.4.2'.4'.2''-Pentamethoxy-triphenylcarbinol 1755-51-7 C24H26O6
五甲氧红
α-萘黄酮 α-naphtoflavone 604-59-1 C19H12O2
α-萘黄酮
alpha-纳富妥苯 (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon 145-50-6 C27H18O2
alpha-纳富妥苯
N,N'-二苯基联苯二胺 N,N'-diphenyl-p-phenylenediamine 531-91-9 C24H20N2
N,N'-二苯基联苯二胺
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
4,5-二羟基-3,6-双[(2-磺基苯基)偶氮]-2,7-萘二磺酸
3,8-二溴菲罗啉 3,8-dibromo-1,10-phenathroline 100125-12-0 C12H6Br2N2
3,8-二溴菲罗啉
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
3,3,5,5-四溴酚酞乙酯钾盐
2-硝基苯胺 2-nitro-aniline 88-74-4 C6H6N2O2
2-硝基苯胺
2,9-二溴-1,10-菲罗啉 2,9-dibromo-1,10-phenanthroline 39069-02-8 C12H6Br2N2
2,9-二溴-1,10-菲罗啉
2,5-二巯基噻二唑 2,5-Dimercapto-1,3,4-thiadiazole 1072-71-5 C2H2N2S3
2,5-二巯基噻二唑
2,2'-联吡啶 [2,2]bipyridinyl 366-18-7 C10H8N2
2,2'-联吡啶
1-萘酚酞 α-naphtholphthalein 596-01-0 C28H18O4
1-萘酚酞
1,3,5-三硝基苯 TNB 99-35-4 C6H3N3O6
1,3,5-三硝基苯
1,10-菲罗啉 1,10-Phenanthroline 66-71-7 C12H8N2
1,10-菲罗啉
—— 1(3H)-Isobenzofuranone, 3,3-bis(4-hydroxyphenyl)-, disodium salt 518-51-4 C20H12Na2O4
1(3H)-Isobenzofuranone, 3,3-bis(4-hydroxyphenyl)-, disodium salt
—— Benzoic acid, 2-[[[(2-hydroxy-5-sulfophenyl)azo]phenylmethylene]hydrazino]- 62625-22-3 C20H16N4O6S
Benzoic acid, 2-[[[(2-hydroxy-5-sulfophenyl)azo]phenylmethylene]hydrazino]-
—— (2,4-Diaminophenyl)-(4-ethoxyphenyl)iminoazanium;chloride 2313-87-3 C14H17ClN4O
(2,4-Diaminophenyl)-(4-ethoxyphenyl)iminoazanium;chloride
—— 1(4H)-Naphthalenone, 4-[(4-hydroxy-1-naphthalenyl)phenylmethylene]- 145-50-6 C27H18O2
1(4H)-Naphthalenone, 4-[(4-hydroxy-1-naphthalenyl)phenylmethylene]-
—— p-Naphtholbenzein 145-50-6 C27H18O2
p-Naphtholbenzein
—— 4-(2-pyridylazo)resorcinol 1141-59-9 C11H9N3O2
4-(2-pyridylazo)resorcinol
—— 518-51-4 C20H14NaO4
—— 2,4,6(1H,3H,5H)-Pyrimidinetrione, 5,5-dihydroxy-, trihydrate 5629-46-9 C4H10N2O8
2,4,6(1H,3H,5H)-Pyrimidinetrione, 5,5-dihydroxy-, trihydrate
—— alizarin yellow GG 584-42-9 C13H8N3O5*Na
alizarin yellow GG
—— methyl red 845-10-3 C15H14N3O2*Na
methyl red
—— m-Cresol purple (sodium) 62625-31-4 C21H17NaO5S
m-Cresol purple (sodium)
—— 2-Carboxy-2-hydroxy-5-sulfoformazylbenzene sodium salt 135-52-4 C20H16N4O6S
2-Carboxy-2-hydroxy-5-sulfoformazylbenzene sodium salt