IRON RUST. 307 



No. 6. — Rust from old wr ought-iron tyre. 



Weight of powder = 4"691 grammes. In separating this 

 under water a certain amount of fine powder was obtained 

 in suspension, and this apparently was not attracted ; at any 

 rate it could not readily be removed from the water by the 

 magnet, but on evaporating it down on a sand bath it was 

 found to be wholly lifted by the magnet. 



Another specimen of the same, weighing 9'856 grammes, 

 was crushed in an agate mortar, dried in water oven, and 

 also found to be wholly lifted by the magnet. 



No. 7. — Rust from old sheet iron barrow, probably formerly 

 galvanised. 



The scales showed well defined north and south poles. 



146 grammes were crushed and passed through a No. 30 

 sieve'. The whole of the dark brown powder was found to 

 be attracted by the magnet. 



No. 8. — Rust from old disused boiler-plate chimney. 



60 grammes were crushed and passed through a No. 30 

 sieve, and yielded a dark brown powder, the whole of which 

 was magnetic. The scales were also polar. 



This example is not of so much value as the others, 

 because it might be thought that the scale consisted of or 

 contained magnetic oxide (FegO^) which had been formed at 

 a high temperature, although personally I am satisfied that 

 it was formed by the ordinary process of atmospheric rusting. 



No. 9. — Rust from old tinned-iron can. 



All traces of metallic tin had disappeared. VQ grammes 

 were crushed and passed through a No. 60 sieve ; the light 

 brown powder was wholly lifted by the magnet. 



No. 10. — Rust from scrap heap. 



In the form of cakes, from ^"5^ to \ inch in thickness, and 

 of several inches superficial area. The cakes were of the 

 usual dark brown colour, but with soft powdery yellow- 

 ochrey patches and cones or excrescences. These were 

 detached and ground separately in an agate mortar, and 

 found to be nearly free from magnetic particles, but the soft 

 black powder found under the excrescences or pimples was 

 highly magnetic. 



