_Symptoms._--Poisoning with muriatic acid is so rare that the symptoms have not been well studied, but they do not appear to differ much from those produced by the action of the other acids. It does not stain the skin, but may darken the mucous membranes. The fumes are apt to attack the air-passages. _Chemical Analysis._--The acid will have to be examined under the following heads: 1. Simple, concentrated acid. 2. Dilute acid. 3. Mixed with organic liquids, food, &c. 4. On the clothes of the person injured. I. Concentrated Acid 1. _Action on Organic Matter._--The strong acid tinges most organic tissues, when immersed in it, a _yellow colour_. The stains on black cloth are at first distinctly _red_, becoming reddish-brown after a few days. 2. _Action on Metals._--This acid does not act on copper or mercury, even when boiled with them, and this distinguishes it from the other acids. 3. Hydrochloric acid, added to peroxide of manganese and then warmed, gives off chlorine gas, detected by its greenish-yellow colour and suffocating odour. The vapour thus produced bleaches litmus paper, and causes a blue coloration on starch paper moistened with iodide of potassium. II. Dilute Acid 1. Decomposes alkaline carbonates, chlorides being formed which, when heated in the solid state with strong sulphuric acid and peroxide of manganese, evolve chlorine gas, known by the before-mentioned tests. 2. _Precipitation of Chloride of Silver._--A white curdled precipitate of chloride of silver is thrown down when a solution of nitrate of silver is added to hydrochloric acid. This precipitate becomes grey on exposure to light. If a portion of the precipitate be added to ammonia it will dissolve; another portion, when boiled with nitric acid, is unaffected; and a third portion, ignited in a capsule, becomes converted into a horny mass. In any case where there is a doubt as to whether the hydrochloric acid exists in the free state, or is only present in the form of chlorides, the following test should be resorted to, which will not only discriminate between the two forms, but give the relative amount of each present: Take two equal measures of the acid liquid. Precipitate one with nitrate of silver, after the addition of nitric acid, and weigh the precipitate. Evaporate the second portion of the acid liquid to dryness, and dry the residue in a water bath; dissolve this residue in distilled water, and treat the solution with nitrate of silver as before, weighing any precipitate which occurs. The weight of chloride of silver obtained from the first portion of the liquid will give all the hydrochloric acid present, both in the free state and in combination; while the weight of the silver precipitate in the second portion of liquid only gives the chlorides, all free--hydrochloric acid having passed off during the process of evaporation. III. Mixed with Organic Liquids, &c.