Hydrochloric Acid
The solution is placed in a retort provided with a receiver and distilled until the residual fluid assumes a pasty consistence: the operation is then discontinued. If hydrochloric acid be present in the materials under examination, the distillate will have an acid reaction, and, upon addition of solution of nitrate of silver, a white precipitate, which is easily soluble in ammonia but insoluble in nitric acid and in short possesses all the properties of chloride of silver, will be formed.