Abstract: In the nitration of a volatile aromatic compound wherein the compound is reacted with a liquid nitrating agent thereby to effect nitration and to produce a waste gas containing some of the aromatic compound, nitrogen oxides and nitric acid, the improvement which comprises contacting the waste gas with fresh nitrating agent thereby to remove the aromatic compound from the gas into the nitrating agent, and thereafter using such nitrating agent to effect subsequent nitration.

Abstract: A process for treating final acid obtained in forming a nitrate of a polyhydric alcohol, said final acid comprising a mixture of sulfuric acid, nitric acid, water and said nitrate, said process comprising mixing said final acid with an aromatic nitro compound, allowing said mixture to stratify whereby said nitrate is dissolved into said aromatic nitro compound as one layer and there is another substantially nitrate-free waste acid layer comprising sulfuric acid, nitric acid and water, and separating said layers. Preferably the nitrate is trinitroglycerine and the aromatic nitro compound is dinitrotoluene. The waste acid layer advantageously is partially used to form additional dinitrotoluene and is partially mixed with fresh final acid since its presence serves to stabilize such final acid by preventing any settling out of trinitroglycerine, presumably by the action of the small amount of dinitrotoluene which may be present in said waste acid.