396 STUDIES FOR STUDENTS 



nickel present. In hardness and tenacity the nickel-iron of differ- 

 ent meteorites varies greatly. That of some meteorites is harder 

 than steel, that of others softer than wrought iron. That of 

 some meteorites is so brittle as to break in pieces with a blow of 

 the hammer, that of others so malleable that it can be worked 

 into implements of various shapes. Nickel-iron is strongly mag- 

 netic and some iron meteorites exhibit polarity due perhaps to 

 induction of the magnetism of the earth. The specific gravity 

 of nickel-iron ranges between 7.6 and 7.9. It is dissolved at 

 ordinary temperatures by the common acids, by solutions of 

 copper sulphate, by copper chloride, by mercuric chloride, by 

 bromine water, by copper ammonium chloride, and by a few 

 other reagents. Some masses of nickel-iron when placed in 

 neutral solutions of copper sulphate reduce the latter, while 

 others do not. The former are known, according to the terms 

 first used by Wohler, as active, the latter as passive irons. 

 Nickel-iron oxidizes rapidly when exposed to the atmosphere, 

 the rapidity decreasing, however, with increase in the percentage 

 of nickel. In regard to the manner of occurrence of the nickel- 

 iron it may be noted that in the iron meteorites it forms a com- 

 pact mass except in so far as it is interrupted by inclusions of 

 other minerals. In the iron-stone meteorites all gradations 

 occur from a continuous network to isolated grains. In the 

 stone meteorites it is present in the latter form. A more or 

 less lineal arrangement of these grains, recalling Widmanstatten 

 figures, is often observed in the stone meteorites. When the 

 substance occurs in grains, whether large or small, the shape of 

 these is usually very uneven, being sometimes more or less 

 rounded but generally irregularly branching. Sometimes regular 

 forms such as cubes and octahedrons may be observed. In the 

 Ochansk meteorite, von Siemaschko observed actual crystals 

 made up of a combination of the cube, octahedron, dodecahedron, 

 and a tetrahexahedron. Other cuboidal forms have been 

 observed. The two or possibly three subordinate alloys (kama- 

 cite, taenite, and plessite) of which nickel-iron is composed have 

 been described in a previous article and their composition given. 



