Question

In which temperature Boric oxide start melting?

• A. $800^{\circ}C$
• B. $300^{\circ}C$
• C. $700^{\circ}C$
• D. $900^{\circ}C$

Hint:

Logic Tip: Boric oxide is a super-low melter used to replace lead. It begins softening and melting exceptionally early, around $300^{\circ}C$.

Answer 1

The Correct Option is B

Concept:
Boric oxide ($B_2O_3$) acts as a powerful glass former and flux in ceramic glaze chemistry, significantly lowering the melting point of glazes.

Step 1:
Boron is unique because it is both a flux (melter) and a glass former (like silica). It is heavily used in low-fire glazes (like earthenware) to achieve a glossy melt without using toxic lead.

Step 2:
Pure boric oxide has an extremely low melting point and glass transition temperature compared to other ceramic oxides.

Step 3:
While its exact behavior depends on the mixture, pure $B_2O_3$ has a glass transition temperature around $300^{\circ}C$ and begins to heavily soften and melt into a liquid state between $300^{\circ}C$ and $450^{\circ}C$.

Step 4:
The temperatures $700^{\circ}C$, $800^{\circ}C$, and $900^{\circ}C$ are much higher than the actual threshold where boric oxide begins to melt and become active.

Step 5:
Because it is a remarkably low-temperature material, $300^{\circ}C$ is the correct starting point for its melting phase. \[ \boxed{\text{(2) } 300^{\circ}C} \]