Question

Which of the following is a mordant dye?
A.Aniline black
B.Congo red
C.Alizarin
D.Indigo

Answer 1

Hint: To answer this question you must recall the different types of dyes. Mordant dyes are substances that are used to dye fabrics by forming a coordination bond with them.

Complete step by step answer:
Mordant is a substance that is used in combination with a dye to carry out the dyeing process. It may be used for either dyeing of fabrics or for the intensification of stains in cells and tissues. A mordant is responsible for the coordination bond formed that attaches the dye to the fabrics. It is mostly a polyvalent metal ion like chromium (III). The coordination complex formed by the mordant with the dye is colloidal.
Aniline black is a type of aniline dye.
Congo red is a type of an azo dye.
Alizarin is a type of a mordant dye.
Indigo is a type of a vat dye.
Alizarin is used in biochemical assay to quantitatively determine the presence of calcific deposition by the cells of an osteogenic lineage by colorimetry. It is also used to stain synovial fluid to test it for the presence of basic calcium phosphate crystals. It also has applications in geology where it is used as a stain to indicate the minerals of calcium carbonate, namely calcite and aragonite.

Hence option C is correct.

Note:
Alizarin is the key ingredient in the production of madder lake pigments also known as Rose madder and Alizarin crimson to painters. Alizarin has a deep red color, but the term is also used in the name for many similar non-red dyes, namely Alizarine Cyanine Green and Alizarin Brilliant Blue.