Pyrogallol red
Structural formula | |||||||||||||||||||
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General | |||||||||||||||||||
Surname | Pyrogallol red | ||||||||||||||||||
other names |
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Molecular formula | C 19 H 12 O 8 S | ||||||||||||||||||
Brief description |
reddish brown solid |
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properties | |||||||||||||||||||
Molar mass | 400.36 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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Melting point |
> 300 ° C |
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solubility |
soluble in water |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Pyrogallol red is a triphenylmethane dye and belongs to the group of sulfonphthaleins. It is used as an indicator in complexometry . Its phthalein analogue is pyrogallolphthalein . The bromopyrogallol red can be represented by bromination .
Properties and use
Pyrogallol red is mainly used to determine bismuth in a nitric acid medium (pH 2-3); the color changes from red to orange-yellow. Lead can also be determined in a weakly acidic medium in the presence of a sodium acetate buffer. The determination of nickel and cobalt can be carried out in a weakly alkaline medium (pH 8.9; NH 3 / NH 4 + ). Pyrogallol red is poorly soluble in water, a solution of 0.05 g in 50% ethanol is used for titration.
Individual evidence
literature
- Complexometric determinations with Titriplex. (Ed. by E. Merck, Darmstadt)