Gentian violet.
Methyl violet.
Fuchsine.
Bismarck brown.
The following solutions of these dyes are used:—
1. Saturated alcoholic solutions which may be kept in stoppered bottles.
2. One per cent. aqueous solutions. These must be freshly made each time of using.
In filtering either alcoholic or aqueous solutions it is well to moisten the filter paper beforehand with alcohol or water as the case may be.
The following special solutions will also be wanted:—
Löffler’s methylene blue.—In this solution a weak solution of caustic potash is employed as a mordant:—