Indicator is a type of auxiliary chemical reagent. It can be used to test the acidity‑alkalinity of solutions, indicate titration endpoints in titrimetric analysis, and detect harmful substances in environmental monitoring. Under certain medium conditions, it may change color, produce turbidity or precipitate, or generate fluorescence. Depending on the chemical reaction involved, indicators are classified into acid‑base indicators, redox indicators, metal‑ion indicators, adsorption indicators, fluorescent indicators and so on. Among them, acid‑base indicators are the most widely‑used.In titrimetric analysis, a sample solution is titrated with a standard solution. When the reaction is complete, the two substances react in equivalent amounts, and this point is defined as the equivalence point. Accurate determination of the equivalence point is critical for titration analysis. An abrupt color change of the indicator usually serves as the signal for reaching the equivalence point. During titration, the concentrations of the sample and standard solution continuously change with the addition of titrant. Near the equivalence point, ion concentrations vary sharply, accompanied by solution color change or precipitate formation. If the standard or sample solution is colored, it can act as an indicator itself, such as potassium permanganate.
Calcon, also known as Calconcarboxylic Acid; Calcon Indicator; Calcium Carboxylate; Calcium Indicator;3‑Hydroxy‑4‑[(2‑hydroxy‑4‑sulfo‑1‑naphthyl)azo]‑2‑naphthalenecarboxylic acid;
1‑(2‑Hydroxy‑4‑sulfo‑1‑naphthylazo)‑2‑hydroxy‑3‑naphthoic acid;2‑Hydroxy‑1‑(2‑hydroxy‑4‑sulfo‑1‑naphthylazo)‑3‑naphthoic acid;Calconcarboxylic Acid Indicator. Calcium Red Indicator (NN) consists of calcium indicator (Calcon / Calconcarboxylic Acid), methanol and other components. It is a commonly‑used metal‑ion indicator (calcium‑ion indicator) for complexometric titration experiments, with an endpoint color change from red to blue.NN shares similar properties with Eriochrome Black‑T. Its color varies with pH values: it appears blue at pH 8‑13, and pink when pH＞13.2 or pH＜7.5.Calcon indicator forms a red complex with Ca²⁺. At pH=13, it can be applied for the determination of calcium in calcium‑magnesium mixtures, and the endpoint changes from red to blue with sharp color transition. Under this condition,Mg²⁺ precipitates as Mg(OH)₂ and will not be titrated. Like Eriochrome Black‑T, calcon indicator is also subject to indicator‑blocking by ions such as Cu²⁺, Ni²⁺, Co²⁺, Al³⁺, Fe³⁺ and Ti⁴⁺. Sodium sulfide, potassium cyanide or triethanolamine can be used as masking agents to eliminate this interference.
Operating Procedure (For Reference Only):
1. Operate in accordance with specific laboratory requirements. Generally, add 1 drop (0.05‑0.1 mL) of indicator to every 10 mL of test solution.
2. Color change at titration endpoint: Red → Blue.
Precautions:
1. Excessive dosage of indicator will shift its color‑change range toward lower pH values. Meanwhile, indicator color‑consumption of titrant will increase measurement error and reduce the sharpness of color transition.
2. Recommended dosages differ for various indicator types. For acid‑base indicators, 1 drop (0.05‑0.1 mL) of indicator is generally added to each 10 mL of test solution.
3. For your safety and health, please wear a lab coat and disposable gloves during operation.
4. Use this reagent as soon as possible after opening to avoid adverse effects on subsequent experimental results.
5. This product is intended for research‑use only. It is not suitable for clinical diagnosis or other applications.
