For hardening the blastoderm I have employed, as usual, chromic acid, and also gold chloride.
Another example is the gold chloride familiar to photographers.
To this is slowly added one grain of gold chloride in half an ounce of water.
It forms a double salt with gold chloride, sparingly soluble in water.
The stains of most importance are carmine, methylene blue, hmatoxylin, gold chloride and Bismarck brown.
The mercury vapour reduces the gold chloride, and gold is deposited as a bluish-violet stain; 1⁄10 mgrm.
It forms crystalline salts with platinic chloride, with gold chloride, with mercuric chloride, and with zinc chloride.
Then take two drams of the gold chloride solution and dilute with an ounce of water, and add slowly with stirring as before.
It also gives a difficultly soluble salt with gold chloride.
It gives a precipitate with gold chloride, reducing the gold; also one with mercuric chloride easily soluble in hydrochloric acid.