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Names | |
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IUPAC name (3E)-3-[(2,4-Dinitrophenyl)hydrazono]-4-oxonaphthalene-2,7-disulfonic acid | |
Other names Nitrazine yellow; Phenaphthazine | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
PubChem CID | |
UNII |
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Properties | |
C16H10N4O11S2 | |
Molar mass | 498.40 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Nitrazine or phenaphthazine is a pH indicator dye often used in medicine. More sensitive than litmus, nitrazine indicates pH in the range of 4.5 to 7.5. Nitrazine is usually used as the disodium salt.
Nitrazine(pH indicator) | ||
below pH 4.5 | above pH 7.5 | |
4.5 | ⇌ | 7.5 |
This test, however, can produce false positives. If blood gets in the sample or if there is an infection present, the pH of the vaginal fluid may be higher than normal. Semen also has a higher pH, so recent vaginal intercourse can produce a false reading.