Difference between revisions of "Gallein"
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== Description == | == Description == | ||
| − | Brownish-red crystals used as a red dye. Gallein was first prepared by Baeyer in 1871 by mixing [ | + | Brownish-red crystals used as a red dye. Gallein was first prepared by Baeyer in 1871 by mixing [[pyrogallic acid]] with [[phthalic anhydride]]. Gallein was used as a dye in the late 19th century but was soon replaced by [[aniline dye|aniline]] colors. It produces a bluish-red color with [[alumina]] or iron mordants and a dark violet with lead and tin mordants. Gallein is also used as an acid-base indicator and as a detection reagent for phosphates. |
== Synonyms and Related Terms == | == Synonyms and Related Terms == | ||
Revision as of 14:01, 15 January 2014
Description
Brownish-red crystals used as a red dye. Gallein was first prepared by Baeyer in 1871 by mixing Pyrogallic acid with Phthalic anhydride. Gallein was used as a dye in the late 19th century but was soon replaced by aniline colors. It produces a bluish-red color with Alumina or iron mordants and a dark violet with lead and tin mordants. Gallein is also used as an acid-base indicator and as a detection reagent for phosphates.
Synonyms and Related Terms
3',4',5',6'-tetrahydroxyfluoran; pyrogallolphthalein; CI 45445; mordant violet 25
Other Properties
Insoluble in cold water, benzene, chloroform. Slightly soluble in hot water, ether. Soluble in alkalis, alcohol, acetone.
As an indicator, brownish-yellow below pH=3.8; red above pH 6.6
| Composition | C20H12O7 |
|---|---|
| CAS | 2103-64-2 |
| Molecular Weight | mol. wt. = 364.31 |
Hazards and Safety
Inhalation, ingestion or skin absorption may be harmful.
Sigma Chemical: MSDS
Authority
- The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 4362
- F. Crace-Calvert, Dyeing and Calico Printing, Palmer & Howe, London, 1876