IRON RUST. 311 



Experiment No. 1. — A hole was punched in each strip 

 and a bundle of them suspended by a bright iron wu'e out- 

 side a window, on September 11, 1891, when they weighed 

 456 grammes. On February 16, 1892, i.e. after 19 weeks' 

 exposure, these were scraped with a horn spatula and 2" 14 

 grammes of rust obtained, of which only "184 grammes, or 

 8"6 per cent., was non-magnetic. The colour of rust was 

 ochrey outside and black inside. 



Experiment No. 2. — A second lot of 457 grammes was 

 suspended in the same way on the roof of the Chemical 

 Laboratory. On February 16, 1892, i.e. after 19 weeks' 

 exposure, these also were scraped with a horn spatula and 

 yielded 6-6 grammes of rust, of which only -775 was 

 non-magnetic, or 11*7 per cent. The rust was of the usual 

 colour outside, but nearly black underneath. 



Experiment No. 3. — A third bundle of sheets, weighing 

 453 grammes, was placed in a 24-oz. stoppered cylinder of 

 boiled distilled water on September 11, 1891. This iron was 

 scraped on May 27, 1892, after 36 weeks' action, with a horn 

 spatula, and brushed with a new nail-brush, and yielded 

 2'604 grammes of blackish oxide, of which the whole was 

 attracted by the magnet. 



Experiment No. 4. — A further bundle of 453 grammes 

 was placed in a similar stoppered cylinder of unboiled dis- 

 tilled water, treated in the same way as Nos. 2 and 3, and on 

 the same dates. Yielded -694 grammes of dark brown 

 oxide, wholly lifted by the magnet. 



Experiment No. 5. — 453 grammes of strips were similarly 

 placed in a cyhnder of tap water on May 27. They were 

 taken out, dried on a water bath, scraped with a horn spatula, 

 and carefully brushed ; the rust weighed -538 grammes ; it 

 was of a dark brown colour, and wholly attracted. 



Experiment No. 6. — A bundle of strips, weighing 4^9 

 grammes, was placed in cyhnder of distilled water charged 

 with carbon dioxide. Treated in the same way as the others 

 and on the same dates. This yielded *545 grammes of a 

 dark yellowish brown colour. Some of the oxide in this case 

 was in the form of brown iridescent films floating in the 

 water. These brown films were also found to be magnetic 

 after boiling ; they were also found to yield no blue coloura- 

 tion with potassium ferricyanide added to thin solution in 

 hydrochloric acid. In all the other cases (1 to 5) the loose 

 oxide floating in the water and attached to the iron was 

 black. 



