[Footnote 23: ‘Journ. of the Chem. Soc.,’ v, 173.] The presence of the alkaloids and their salts, in clear solutions, may be thus determined:—— I. (Fresenius).——1. The solution is rendered very slightly alkaline with dilute solution of potassa or soda, added drop by drop:—— a. No precipitate is formed; total absence of the alkaloids. (See 4, _below_.) b. A precipitate is formed:——solution of potassa or soda is added, drop by drop, until the liquid exhibits a strong alkaline reaction:—— α. The precipitate redissolves; absence of Brucia, Cinchonia, Narcotina, Quina, Strychnia, and Veratria; probable presence of MORPHIA. β. Precipitate does not redissolve, or not completely; probable presence of one or more of the first six of the above-named alkaloids:——the fluid is filtered from the precipitate, mixed with either bicarbonate of soda or of potassa, gently boiled nearly to dryness, and treated with water. If it dissolves completely; absence of morphia; an insoluble residue indicates MORPHIA. 2. The precipitate 1. _b._ β. is washed with cold distilled water, dissolved in a slight excess of dilute sulphuric acid, neutralised with a saturated solution of bicarbonate of soda, and allowed to repose a few hours:[24]—— [Footnote 24: Before setting the glass aside the liquor should be well mixed, and the glass stirrer vigorously rubbed against the sides of the vessel.] _a_. No precipitate; absence of Cinchonia, Narcotina, and Quina:——the solution is gently evaporated nearly to dryness, and treated with cold water:——if it dissolves completely, pass on to 4; if there is an insoluble residue, it may contain Brucia, Strychnia, or Veratria. (See 3.) _b._ A precipitate:——the filtered fluid is treated as directed at 2 _a_.; the precipitate is washed with cold distilled water, dissolved in a little hydrochloric acid, ammonia is added in excess, and subsequently a sufficient quantity of ether, agitation being had recourse to:—— α. The precipitate formed by the ammonia redissolves completely in the ether, and the clear fluid separates into two layers; absence of Cinchonia; probable presence of QUINA or NARCOTINA. β. The precipitate produced by the ammonia does not redissolve in the ether, or not completely; probable presence of CINCHONIA, and perhaps also of Quina or Narcotina. The filtered liquid may be tested for these alkaloids as at _a_. 3. The insoluble residuum after the evaporation of the solution 2. _a._, or of the filtrate 2. _b._, is now dried in a water bath, and digested with absolute alcohol:——