Acid-base indicator, pH value range 3.1 (red) - 4.4 (yellow), determination of the alkalinity of most mineral acids, strong bases and water. The capacity is determined by tin (Sn2+ (2+ superscript) when hot makes the methyl orange fade). Attenuating indicator for strong reducing agents (Ti3+(3+ superscript), Cr2+(2+ superscript) and strong oxidizing agents (chlorine, bromine). Spectrophotometric determination of chlorine, bromine and bromide ions. Can be used with sodium indigo disulphonate Or bromocresol green constitutes a mixed indicator to shorten the discoloration domain and improve the sharpness of discoloration. Redox indicator, such as potassium bromate titration of trivalent arsenic or antimony.

Function:
1.Methyl orange is a commonly used acid-base titration indicator in analytical chemistry and is not suitable for use as an organic acid compound drop.
The indicator. The pH of the 0.1% aqueous solution is 3.1 (red) ~ 4.4 (yellow), which is suitable for titration between strong acid and strong base and weak base. It is also used for spectrophotometric determination of chlorine, bromine and bromide ions, and for biostaining.
2.Methyl orange has been used as a pH control for chemical reactions in laboratory and industrial and agricultural production, as well as acid-base titration analysis of chemical products and intermediates. A disadvantage of the methyl orange indicator is that the yellow-red color is more difficult to identify and has been replaced by a wide range of indicators (see "Phenolphthalein"). Methyl orange is also an azo dye that can be used to print textiles.