Ammonium and ammonia salts are readily detected in very minute traces by Nessler's solution addition, which gives a distinct yellow coloration in the presence of the slightest trace of ammonium or ammonia salts. The amount of ammonia present in the ammonium salts is quantitatively estimated by salt distillation with potassium or sodium hydroxide, the ammonia evolved being absorbed in a known and considerable volume of standard sulfuric acid, and then the excess of acid can be determined volumetrically.