Pyrogallol red
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| General | |||||||||||||||||||
| Surname | Pyrogallol red | ||||||||||||||||||
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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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| 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)