(a.) Solutions in Distilled Water.
Several saline substances are directed to be dissolved in distilled water. In such cases 10 grains by weight of the salt must be dissolved in a sufficient quantity of the water, and the volume of the solution increased to 100 or 1,000 minims, as the case may be; and no such preparation can be considered satisfactory unless the solution is perfectly free of all sediment, and continues clear and transparent. If, after a time, it deposits any crystals, or if any of the salt effloresces around the neck of the bottle, or if a fibrous-looking sediment conferva) appears in the solution, or if the solution changes colour materially, in each and all these instances the preparation should be rejected and a fresh quantity made. Since many aqueous solutions do not keep for any length of time, it is well to dissolve only a sufficient quantity of the salt at a time to meet the current demand, and to make this first decimal or centesimal attenuation again and again, as required. The salt itself should be obtained in sufficient quantity to last for some time, except in the case of perishable compounds, so as to avoid the necessity for repeated analyses, to insure the purity of the articles.
(B.) Solutions in Alcohol.