* The Dense White Fumes* are sulfur trioxide solid particles,

They prove the removal of Nitric Acid,** HNO _{3}** by Fractional Distillation.

The PbSO_{4} precipitate cannot form if any HNO_{3} is left over from the* Aqua Regia* in the previous procedure. *Aqua Regia* is a mixture of HNO_{3} and HCl.

So, H_{2}SO_{4} is added for two reasons:

1. It provides the **SO _{4}^{-2}** ions to precipitate PbSO

2. It will remove the **HNO _{3}** by Fractional Distillation. In

Since HNO_{3} boils at 130^{o} C, and H_{2}SO_{4 }boils at 338^{o} C, the HNO_{3} will have distilled off when the H_{2}SO_{4} boils.

When H_{2}SO_{4} boils, it decomposes into sulfur trioxide, the **The Dense White Fumes:**** **

**H _{2}SO_{4} -------> SO_{3} **

Hence: * The Dense White Fumes* prove that the HNO

WARNING: * The Dense White Fumes* do NOT prove lead present. They prove that HNO

WARNING: Do NOT confuse steam, H_{2}O_{(g)} with **SO _{3}**