2. Pettijean's process. 1540 grs. of nitrate of silver are treated with 955 grs. of strong solution of ammonia, and afterwards with 7700grs. of water. To this solution, when clear, are added 170 grs. of tartaric acid dissolved in 680 of water, then 152 cubic inches more of water, with brisk agitation. When it has settled, the clear part is poured off; 152 cubic inches of water are added to the sediment, to dissolve as much as possible. The clear fluids are mixed, and again 62 cubic inches of water are added. This is Silvering Solution No. 1. No. 2 is prepared in the same manner, but with twice as much tartaric acid. The glass plate being cleaned, and laid horizontally, an even layer of Solution No. 1 is poured on it, to about the depth of 1/10th of an inch. Heat is then applied by means of a cast-iron water-bath beneath. Bright silver is soon deposited. When the stratum of fluid is exhausted, it is poured off, and solution No. 2 next applied in the same way. The silver surface may be polished, or coated with black varnish.

3. Liebig proposes to silver glass without mercury by a solution of ammonio-nitrate of silver, to which potash or soda is added, and which deposits silver at ordinary temperatures when brought in contact with an acqueous solution of sugar of milk.

4. Mr. Drayton mixes 1 oz. of nitrate of silver, 3 oz. of water, 1 oz. of liquid ammonia, and 3 oz. of spirit of wine, and filters the solution after it has stood 4 hours. To every ounce of the solution he adds 1/4 oz. of grape sugar, dissolved in equal quantities of water and alcohol. The surface to be silvered is covered with this liquid at a temperature of 160° F. maintained till the deposition of silver is complete. When quite dry, the coated surface is covered with mastic varnish. Other substances besides sugar occasion the deposition of silver from the ammoniacal solution; as oil of cassia, oil of cloves, and other essential oils, aldehyde, etc. Unger recommends a strong alcoholic solution of tannin. M. Vohl prefers an alkaline solution of gun-cotton. Dissolve gun-cotton in a solution of caustic potash, pour it into a solution of nitrate of silver, and add ammonia sufficient to redissolve the precipitate. The liquor, being slowly heated in a water-bath, becomes brown, effervesces, and deposits silver of superior brilliancy