What is Hydroxynaphthol blue used for?

What is Hydroxynaphthol blue used for?

Hydroxynaphthol blue is an azo dye. It is used for determining the endpoint in complexometric titrations/Metal Titration.

How do you make Hydroxynaphthol blue indicator?

Dissolve 0.3 g in 100 mL of water, add 10 mL of 1 N sodium hydroxide volumetric solution and 1.0 mL of calcium chloride solution (1 g in 200 mL), and dilute with water to 165 mL.

What is the color of EBT in EDTA experiment?

A variety of indicators can be used for EDTA titrations. In this experiment, we will use Eriochrome black T (EBT) indicator, having the structure shown below.

Why is magnesium added to EDTA?

EDTA Solution The EDTA will dissolve slowly over a period of a half an hour. Magnesium chloride is added to enhance the sharpness of the endpoint (It forms a more stable complex with the indicator).

What is the color of Hydroxynaphthol blue?

Biochem/physiol Actions. Hydroxy naphthol blue disodium salt exists as small blue crystals. It changes color at pH range 12-13 from blue to reddish pink, in the presence of calcium ions and to deep blue in the presence of disodium ethylenediaminetetraacetic acid (EDTA).

What is signified with blue colour as the end point in the titration?

Answer: As the stronger ligand EDTA is added, the CaIn+(aq) complex is replaced by the CaY2-(aq) complex which is blue. The end point of titration is indicated by a sharp colour change from wine red to blue. Titration using Eriochrome Black T as indicator determines total hardness due to Ca2+(aq) and Mg2+(aq) ions.

When a drop of EBT added to water shows steel blue colour indicates?

EBT is blue in a buffered solution ( an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa) at pH 10. It turns red when Ca2+ ions are added. The ions involved in water hardness, i.e. Ca2+(aq) and Mg2+(aq) change the steel blue colour of EBT indicator into wine red colour.

What is pH range of phenolphthalein?

Phenolphthalein is an acidic indicator which is used in the pH range of 8. 2−10.

Which colour appears at the end of EDTA titration?

The endpoint of a complexometric EDTA titration using either Calmagite or EBT as the indicator is detected as the colour changes from pink to blue.

What is the role of EBT in titration?

EBT binds with free metal ions in the water to form a pink complex. EDTA has a stronger affinity for the metal ions than EBT so when EDTA is added it replaces the EBT and the EBT returns to its blue, uncomplexed color. The blue color is used as the end point in the titration.

Why do we use nh4oh nh4cl buffer in EDTA experiment?

But both EDTA and the indicator are themselves weak acids, therefore a buffer solution such as ammonium hydroxide-ammonium chloride buffer, which is able to maintain a fairly constant pH even when acids and bases are added, is used.

Why pH is maintained in EDTA?

pH 10 buffer is used in EDTA titration because in EDTA Y4- is predominant, and we want Y4- to react with the metal ions that are present in the titration solution. This can be achieved by using a pH 10 buffer.

Why do we use ammonia buffer in EDTA titration?

A buffer solution is used in EDTA titration because it resists the change in pH. This is because all the reactions between the metal ions and EDTA are pH-dependent.

Is thymol blue A acid or base?

weak acid
Thymol blue is another weak acid that is used as an indicator. The fully protonated species (abbreviated H2Thy) is red, the monoprotonated species (HThy-) is yellow, and the fully deprotonated species (Thy2-) is blue.