84 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



IKON DEPOSITED BY ELECTKICITY. 



The following conclusions have been reached in the course 

 of investigations into the characteristics of iron deposited by 

 electricity. First, iron and copper, when deposited, absorb a 

 certain amount of gas, especially hydrogen; second, the vol- 

 ume of the gas absorbed by iron varies between widely ex- 

 tended limits, this, in the case of iron, being sometimes as 

 much as 185 times its volume; third, absorption of gas takes 

 place principally in the layers which are deposited first ; 

 fourth, when such iron is heated, the disengagement of the 

 gas commences below the temperature of 212 degrees. At 

 this temperature it is principally hydrogen that is separated. 

 3 ., January ^ 1872, 33. 



METALLIC POTASSIUM. 



Professor Dolbear obtains metallic potassium by a new 

 process, which is likely to prove of much commercial value. 

 He first forms sulphide of potassium by treating dissolved 

 sticks of caustic potassa with sulphureted hydrogen, and 

 subsequently evaporating until the mass is solid in cooling. 

 This mass is then mixed with somewhat more than its bulk 

 of iron filings, and subjected to distillation, the product being 

 run off into petroleum. 3 A, May 4, 1872, 382. 



NITRATE OF SILVER FROM SILVER ALLOY. 



Mr. R. Palm, of Russia, has succeeded in obtaining pure ni- 

 trate of silver from the metal alloyed with copper by a very 

 quick and simple process. He dissolves the alloy in nitric 

 acid, evaporates to the consistency of thick oil (not to dry- 

 ness), and then adds concentrated nitric acid. The silver salts 

 precipitate in crystals, while the copper remains in solution. 

 The crystals have to be repeatedly washed in concentrated 

 nitric acid, and then they contain no trace of copper. 14 C 

 vol. 204. 



IMPROVEMENT IN NICKEL PLATING. 



An English patent, for the purpose of improving the adhe- 

 siveness of the nickel deposit upon iron or steel by the gal- 

 vanic process, recommends the addition of a small quantity 

 of an acetic, citric, or (best of all) tartaric salt of potash, soda, 



