516 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



of nitrate of nickel in 4 of liquid ammonia and 150 of water, 

 in which 50 parts of sulphate of soda have been dissolved. 

 With a moderate current the operation is completed in a 

 few minutes. When the film of nickel is of sufiicient thick- 

 ness the objects are withdrawn from the bath and dried witli 

 sawdust. 3 ^, VI., 523. 



PEODUCTION OF A BROWNISH PATINA ON ZINC. 



A solution of molybdic acid, or of molybdate of ammonia, 

 in very dilute aqua regia, or of molybdic acid in excess of 

 very dilute solution of caustic soda, according to Professor 

 Kletzinsky, produces a very pleasing, adherent, brownish 

 patina, inclining to iridescence, upon articles of cast zinc im- 

 mersed in it. 13 (7, 1875, 1555. 



COATING MIRROES WITH AN ALLOY OF GOLD AND PLATINUM. 



Five hundred grains of spongy platinum are dissolved in 

 50 cubic centimeters of hydrochloric and 50 of nitric acid, 

 and the mass is evaporated to dryness. It is then powdered 

 and digested with 2000 grains of essence of lavender, 100 

 grains of turpentine, and 25 grains of sulphuretted turpen- 

 tine resin {haume de ^oufre terebenthine). Thirty grains of 

 gold, made into chloride, are dissolved in 500 cubic centim- 

 eters of water and an equal amount of ether. The liquid 

 is shaken, and the ethereal solution added to the platinum 

 and allowed to evaporate spontaneously. Fifty grains of 

 litharge, fifty grains of lead borate, and 100 grains of laven- 

 der-oil are then added, and the mixture is shaken, after 

 which the mirror is coated with it, and kept at a red heat 

 until the composition is burned in. 21 ^1, XI., 928. 



NICKEL-PLATING SOLUTION. 



Hesz prepares a nickel-plating solution that yields beauti- 

 ful results, by mixing the liquid obtained by evaporating a 

 solution of one-half ounce of nickel in aqua regia to a pasty 

 mass, and dissolving it in one pound of aqua ammonia, with 

 that obtained by treating the same quantity of nickel with a 

 solution of two ounces of cyanide of potassium in a pound 

 of water. More cyanide of potassium renders the deposit 

 whiter, and more ammonia renders it grayer. 18 C, VL, 

 185. 



