178 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



purposes. That iron may be made to combine with mercury- 

 is a fact discovered by Sir Humphrey Davy, whose process 

 consists in immersino: sodium amalo:am in a saturated solu- 

 tion of ferrous chloride or sulphate. Cailletet, in 1857, show- 

 ed that iron may be coated with mercury by means of am- 

 monium amalgam, or by means of electrolysis. As the iron 

 in both cases does not amalgamate till hydrogen appears, 

 Cailletet concludes that the effect is due to the nascent hy- 

 drogen. Desiring to test the soundness of Cailletet's theory, 

 Casamajor placed mercury in a beaker glass, covered it with 

 acidulated water, and introduced a horse-shoe nail of Norway 

 iron. Though a moderate escape of hydrogen took place, no 

 trace of amalgamation appeared, even in twenty-four hours. 

 Having to amalgamate a piece of zinc for another experi- 

 ment, he placed the zinc in the beaker glass with the iron. 

 The evolution of hvdrosren from the nail increased at once 

 very perceptibly, and after a short time the nail was found 

 thoroughly amalgamated. Hence all that is necessary is to 

 place the iron in acidulated water in contact with the mer- 

 cury, and to add a few pieces of zinc; in a few minutes the 

 iron will be coated with mercury. Since the zinc is attack- 

 ed only when a more negative metal touches it, the con- 

 sumption is very slight. The coating of mercury thus pro- 

 duced is not a superficial layer; the mercury sinks into the 

 metal, modifying its physical and chemical properties, as is 

 seen on fracture. No alteration in the tenacity of soft iron 

 is observed, while hard-tempered steel has its brittleness 

 much increased. In the voltaic circuit the amalgamated 

 plate is positive to an unamalgamated one, and hence is 

 more rapidly attacked. The quantity of mercury combined 

 with the iron is very small. A piece of sheet-iron, present- 

 ing on both sides a total surface of three square inches, was 

 amalgamated, and left to soak in mercury for over an hour. 

 The mercury was then wiped off very thoroughly and the 

 piece of sheet-iron weighed. The increase over the original 

 weight was three centigrammes, which showed an absorj^tion 

 of mercury equal to a little over four centigrammes per 

 square inch. The increase in weight of this thin sheet of 

 iron was only three and a half per cent. ; yet the fracture was 

 silvery, and globules of mercury stood on the rough edge of 

 the fracture. Platinum, palladium, aluminum, nickel, and 



