Question

Explain borax bead test.

Answer 1

Hint:The borax bead test is used to determine the presence of specific metals in the mineral which is under consideration.
To carry out the test, the bead is first prepared by using the borax, and then the mineral is exposed to the flame by applying a coating on the surface of the bead.

Complete step-by-step answer:The borax bead test is a type of test which is carried out in order to determine the presence of specific metals particularly in salts or minerals. During the exposure of the borax to the flame, a type of bead is formed. On the surface of this bead, a coating of the mineral or the salt under consideration is applied and then that bead is exposed to the burning flame. Then the flame shows characteristic colour which corresponds to specific minerals, or in other words the metal in the mineral is determined by the colour of the flame.
In this test, the oxides of the metal which are present in the minerals react with the borax bead in order to form metaborates. This reaction can be represented by the following equations,
\[N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O\xrightarrow{\Delta }N{{a}_{2}}{{B}_{4}}{{O}_{7}}\xrightarrow{\Delta }NaB{{O}_{2}}+{{B}_{2}}{{O}_{3}}\]
In this reaction as we can see the formation of borax beads is shown, and the end product is the oxide of boron which would be further used to determine the metal in the mineral.
$C{{r}_{2}}{{O}_{3}}+{{B}_{2}}{{O}_{3}}\to Cr{{(B{{O}_{2}})}_{3}}$
In this reaction as we can see the metaborate of the chromium oxide is formed after the oxide of boron reacts with it. This product is green in colour which is the characteristic of the minerals having chromium in it.

Note:The borax bead test is a type of test which is also termed as the blister test. It uses the borax exposed to a flame which results in the formation of a bead.
This bead is then coated with the mineral and exposed to the flame. The colour of this flame tells us the specific metal which is present in the mineral.