_d._ BORIC ACID.--The filtrate from the precipitate of phosphate of alumina is evaporated to dryness, the residue mixed with sulphuric acid and alcohol, and the latter ignited. If the substance contains _boric acid_, the alcohol will burn with a _green_ flame. The _filtrate_, separated from the precipitate produced by the addition of nitrate of baryta, may contain hydrochloric, hydrobromic and hydriodic acids. In order to detect these compounds, some nitrate of silver is added to the solution, and the precipitate that may form carefully washed and decomposed by fusion with potassa. The mass is then dissolved in water, and the solution submitted to the following tests: _e._ HYDRIODIC ACID.--Some starch paste and nitric acid--containing nitrous acid in solution--are added to a portion of the solution: in presence of an _iodide_, the fluid immediately acquires a blue color. _f._ HYDROBROMIC ACID.--In case iodine has not been detected, chlorine water and ether are added to a second portion of the fluid, and the mixture well agitated. If _bromine_ be present, the ether will assume a _brown_ color. In case iodine is also contained in the fluid, and the detection of bromine is desired, it is necessary to acidulate the solution with hydrochloric acid, and then shake it with chloride of lime and bisulphide of carbon. The bisulphide of carbon dissolves the iodine, acquiring a _violet_ color, which disappears upon a renewed addition of chloride of lime; whereas, in presence of bromine an _orange_ coloration remains, even after the disappearance of the iodine reaction. _g._ HYDROCHLORIC ACID.--Since the substance under examination will already contain hydrochloric acid, it is unnecessary, in most cases, to institute a search for this compound. Nevertheless, it may be well to take a quantity of the solution, corresponding to a known weight of the original substance, and precipitate the acid by adding nitrate of silver. The precipitate formed is dried and weighed. It is then heated in a current of chlorine, in order to completely convert it into chloride of silver, and its weight again determined. Only in case the amount of chloride found is very large, is it to be inferred that the poisoning has been caused by hydrochloric acid. _h._ HYDROSULPHURIC ACID.--(_Sulphuretted hydrogen_). If the precipitate produced by nitrate of silver possesses a black color, it may consist of a _sulphide_. Upon treating a portion with solution of hyposulphite of soda, all but the sulphide of silver is dissolved. In case a residue remains, it is calcined with nitrate of soda, and the sulphate formed detected by adding a soluble barium salt to its solution.