| Methyl yellow | |
|---|---|
 |
|
| IUPAC name | p-Dimethylaminoazobenzene |
| Other names | 4-Dimethylaminoazobenzene, N,N-Dimethyl-4-phenylazoaniline, N,N-Dimethyl-4-aminoazobenzene, Butter Yellow, Solvent Yellow 2, C.I. 11020 |
| Identifiers | |
| CAS number | |
| PubChem | |
| EINECS number | |
| RTECS number | BX7350000 |
| SMILES | CN(C)C(C=C2)=CC=C2N=NC1=CC=CC=C1 |
| Properties | |
| Molecular formula | C14H15N3 |
| Molar mass | 225.289 g.mol-1 |
| Appearance | Yellow crystals |
| Melting point |
116 °C (decomp.) |
| Solubility in water | 13.6 mg.l-1 |
| log P | 4.58 |
| Hazards | |
| Main hazards | Toxic (T) |
| NFPA 704 |
 1
2
0
|
| R-phrases | R25, R40 |
| S-phrases | S36/37, S45 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Methyl yellow, or C.I. 11020, is a chemical compound which may be used as a pH indicator.
| Methyl yellow (pH indicator) | ||
| below pH 2.9 | above pH 4.0 | |
| 2.9 | ↔ | 4.0 |
In aqueous solution at low pH, methyl yellow appears red. Between pH 2.9 and 4.0, methyl yellow undergoes a transition, to become yellow above pH 4.0. Additional indicators are listed in the article on pH indicators. As "butter yellow" the agent had been used as a food additive before its toxicity was recognized (Opie EL)
References
- NIOSH Pocket Guide to Chemical Hazards 0220
- Eugene L. Opie. The Pathogenesis of Tumors of the Liver Produced by Butter Yellow. The Journal of Experimental Medicine, Vol 80, 231-246, 1944.
See also
Structuraly similar compounds:
