The suspected acid liquid should be filtered, and then distilled almost to dryness. The portion of the distillate which comes over at first may be thrown away; but the latter portion will give all the reactions before described for hydrochloric acid, if that be present. Distillation is adopted in the case of this acid, as it is more volatile than either sulphuric or nitric acid. It may be objected that the acid found in the vomited matters is from the gastric juice. In answer to this, it may be stated that the free hydrochloric acid in normal gastric juice is only about five grains in sixteen ounces, an amount which would give but slight reaction with the tests. IV. Stains on the Clothes, &c. The spots produced by the action of the acid on black cloth are at first of a _bright red_ colour, changing in ten or twelve days to reddish-brown. These spots may be cut out and macerated in warm water; the liquid thus obtained then tested by nitrate of silver and the other tests before noticed. Another portion of the cloth should be treated in the same manner, and the resulting liquid tested, as a control against the objection that the acid might have been present in the cloth. Hydrochloric acid has been used to erase writing from paper in attempts at forgery, &c. The paper must be treated in the same manner as mentioned for the cloth, and the tests used. Sometimes oxalic acid is employed for a like purpose, in which case the nitrate of silver will give a precipitate; but the oxalate of silver is soluble in nitric acid; the chloride is not soluble even when boiled. _Fatal Period._--From two or five hours to thirty hours or more. _Fatal Dose._--One fluid drachm to one ounce; recovery has taken place after swallowing two fluid ounces. _Treatment._--The same as for the other acids.