Acid + nitrate

I assume that you're talking about inorganic nitrates, nitrites and sulphides.

If you're adding a strong, non-volatile acid, the respective acid would be produced.
nitrate ----> nitric acid, HNO3
nitrite ----> nitrous acid, HNO2
sulphide ----> hydrogen sulphide, H2S

The nitric acid can be distilled off the reaction mixture under reduced pressure. This is also one way to produce nitric acid (in old days).

Nitrous acid produced would decompose into nitrogen dioxide NO2, nitrogen monoxide NO and water H2O. Cannot be distilled.

Hydrogen sulphide is already a (toxic) gas, need not be distilled.


2012-04-19 14:03:52 補充：
By the way, the acid should be concentrate enough so that the acid displaced does not simply dissolve in the excess water.
The salts are preferably dry solid; sulphide salts could be in aqueous state.

I don't think there will be any reaction taking place for
Acid + nitrate case, silver nitrate solution is always acidified before use!