Modified Methyl Orange Indicator #2, 1 L

$79.17

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Chemicals Volumetric Solutions Laboratory Chemicals by Lab Pro Acids by Lab Pro

Product Number:MO4194-1

What it is. Modified methyl orange indicator #2 is a mixed, or screened, indicator solution that combines methyl orange with a blue dye, supplied in a 1 L size. It gives a sharper, easier-to-read endpoint than plain methyl orange in acid-base titrations near pH 4.
How it is made. Modified methyl orange typically combines methyl orange (sodium salt) with xylene cyanol FF in water. Xylene cyanol is blue at all pH values and screens the orange stage of methyl orange, so the change appears as distinct color shifts rather than a gradual fade.
The color sequence. A typical modified methyl orange is green above about pH 4.6, gray near pH 3.8, and mauve or violet below about pH 2.9. Titrating to the gray point gives a precise, repeatable endpoint that is easier to judge than an orange shade.
Why screened indicators work. Human eyes distinguish complementary color shifts, such as green to gray to mauve, more easily than changes within one color family. Screening also reduces the effect of a slightly colored sample on endpoint judgment.
Standard methods. TAPPI method T 613 and ASTM E 200 reference modified methyl orange for preparing and using indicator solutions, and it is widely used for alkalinity determinations in water, pulp and paper, and process testing.
What #2 indicates. The #2 designation identifies this specific formulation in Lab Pro's product line. Confirm the composition and color transitions on the label or certificate if your method specifies a particular formulation.
Preparing for the titration. Bring samples to room temperature, add the indicator, and titrate against a white background. Approach the endpoint slowly and stop at the first persistent gray. Running a reagent blank corrects for indicator and water contributions.
Using the indicator. Add a few drops per titration, titrate with standard acid until the solution turns gray, and use the same amount for blanks and standards. Pair it with Lab Pro's Hydrochloric Acid 0.1 N (0.1 M), 1 Gallon. For the unscreened form, see Methyl Orange Indicator, 0.1% (w/v) Aqueous.
Where it is used. Modified methyl orange is used to determine total alkalinity in water and wastewater, test pulp and paper liquor, analyze boiler and cooling water, perform carbonate titrations, and teach labs that demonstrate screened indicators.

Technical Specifications

Product	Modified (screened) methyl orange indicator solution
Typical Components	Methyl orange, sodium salt (CAS 547-58-0); xylene cyanol FF (CAS 2650-17-1); water (CAS 7732-18-5). Confirm on SDS
Mixed Indicator CAS (reference)	62758-15-0 (methyl orange-xylene cyanol)
Color Above About pH 4.6	Green
Gray Point	About pH 3.8
Color Below About pH 2.9	Mauve to violet
Appearance	Green liquid
Method References	TAPPI T 613; ASTM E 200
Physical State	Liquid, aqueous solution
Formulation	#2 (Lab Pro designation; confirm composition)
Hazard Profile	Low at indicator strength (confirm on SDS)
Package Size	1 L

Applications / Common Uses

Total alkalinity: Gives a sharp gray endpoint near pH 3.8 to 4.5.
Pulp and paper testing: Supports alkalinity checks on process liquors.
Boiler and cooling water: Monitors alkalinity in industrial water.
Carbonate titrations: Marks carbonate endpoints with strong acid.
Teaching labs: Demonstrates screened indicator chemistry.

Storage, Handling & Shipping

Store tightly closed at room temperature, protected from light and away from strong oxidizers and strong acids. Dispense small amounts into a clean container for use, and never return used indicator to stock.

Incompatible materials: Strong oxidizers and strong acids.
Personal protection: Safety glasses and gloves; the dye stains skin and surfaces.
Spill response: Wipe up with absorbent material and rinse the area with water.
First aid: Eyes: rinse with water for several minutes. Skin: wash with soap and water.

Related Categories & Services

Shop Buffers, Standards & Solutions for related products in this category.
Explore PH Buffers & Test Kits and General Chemistry.
Vendor Managed Inventory (VMI) Program: Lab Pro can stock, track, and replenish this item on site so it never runs out. Contact info@labproinc.com or 888-452-2776 to set up a VMI assessment.

FAQs

What is modified methyl orange?

Modified, or screened, methyl orange is methyl orange combined with a blue dye, usually xylene cyanol FF. The blue dye masks the orange stage, so the indicator changes from green to gray to mauve, giving an endpoint that is easier to see than the gradual orange change of plain methyl orange.

What color is the modified methyl orange endpoint?

Titrate to the gray point, which occurs near pH 3.8 in typical formulations. Above about pH 4.6 the solution is green, and below about pH 2.9 it turns mauve or violet. Stop at the first persistent gray for consistent, repeatable results. Use a white background to judge it.

Why use modified methyl orange for alkalinity?

Its gray endpoint is sharper and less dependent on the analyst's color perception than the orange shades of plain methyl orange. That improves repeatability between analysts and works better in samples with slight natural color, such as surface waters or process liquors. Fewer judgment differences mean better data.

What does #2 mean on this indicator?

The #2 designation identifies this specific formulation in Lab Pro's product line. Because modified methyl orange formulations can differ in dye ratio, confirm the composition and color transitions on the label or certificate if your method requires a specific preparation. Ask Lab Pro for the formulation details if the label does not list them.

Which standard methods reference modified methyl orange?

TAPPI method T 613 and ASTM E 200 reference modified methyl orange, which covers preparation of indicator solutions and is widely used in alkalinity procedures for water and industrial testing. Follow the indicator specified in your method for regulated work. Keep method references on file for audits.