(a) Dissolve 60 grains of silver nitrate in loz. of water, and pour this solution quickly into a boiling solution of 48 grains of Rochelle salt in about 1 oz. of water. On cooling, filter the liquid, and make up to 12 fl. oz. with distilled water, (b) Dissolve 00 grains of silver nitrate in 1 oz. of water, then add ammonia until the precipitate is nearly re-dissolved, and make up to 12 fl. oz., as before. For silvering, equal volumes of these liquids are mixed just previous to using. Another formula is: (a) Dissolve 48 grains of silver nitrate in loz. of distilled water, and add ammonia till precipitate is nearly dissolved, filter the solution, and make up to 12 fl. drachms with water. (6) Dissolve 12 grains of Rochelle salt in 1 oz. of distilled water, boil, and add while boiling 2 grains of nitrate of silver previously dissolved in 1 drachm of water, cool, filter, and make up to 12 fl. drachms. Mix equal proportions as stated above.