D. CHEMISTRY AND METALLURGY. 207 



these specimens, so that Breithanpt has proposed for it the 

 name of iron-platinum. The subject has recently undergone 

 a very thorough study by Daubree, who from his experi- 

 ments upon the native material shows that the presence of 

 iron in proper proportion suffices to account for the polar- 

 ity of the native specimens. He still more firmly establishes 

 his conclusions by artificially producing magnetic platinum, 

 similar to that which occurs in nature. An alloy of 99 parts 

 of iron and one of platinum, after a complete fusion, instead 

 of becoming strongly magnetic, did not give any trace of 

 polarity. Two other alloys, of 75 and 50 parts of iron re- 

 spectively, behaved in very nearly the same manner. Alloys 

 formed some time ago by Berthier, containing 78 parts of 

 platinum and 21 of iron, although imperfectly melted, are, 

 however, susceptible of magnetism. It appears, then, that 

 however pronounced may be the magnetic power of the iron, 

 the alloys where this metal predominates do not acquire polar- 

 ity under the same conditions as do alIo} T s obtained with a 

 smaller quantity of iron. Thus an alloy of 17 parts of iron 

 and 83 jmrts of platinum has very strong magnetic proper- 

 ties, so that we must admit that platinum alloyed with iron 

 in proper proportions becomes exceptionally susceptible of 

 acquiring the magnetic state. In nature this magnetic state 

 would naturally be produced by strong induction, attributa- 

 ble to the magnetic forces of the globe ; and Daubree has 

 therefore, as a last experiment, placed a small bar of the al- 

 loy during its fusion exactly in the plane of the magnetic 

 meridian. As soon as it was solidified, it was inclined so as 

 to be parallel to the inclination needle, until its cooling was 

 complete, and it was then recognized that the bar actually 

 presented at its two extremities very energetic magnetic 

 poles, the upper end being the south pole of the needle, 

 showing that the earth's magnetism had actually produced 

 this effect. On heating the same bar to a red heat, and <riv- 

 ing it the diametrically opposite position during its cooling, 

 it was found that the magnetism of the bar was reversed by 

 the earth's induction. Bulletin Ilebdomadaire, XVI. , 40. 



PRECIPITATION OF METALS BY ZINC. 



Every chemist knows that when metallic zinc is placed in 

 a solution of either copper or silver, the latter metal is pre- 



