ACTION OF MAGNETS ON COMPOUNDS OF THE MAGNETIC METALS. 
43 
the observations of M. Becquerel* and others, found them all, both natural and 
artificial, possessed of magnetic power at common temperatures. I heated them in 
tubes but found them still magnetic, suffering no diminution of the force by such 
temperature as I could apply to them. 
2350. Different specimens of the oxide of nickel were found to present the same 
phenomena. They were magnetic both when hot and cold ; and that heat should 
cause no change in this respect is the more striking, because the hot oxide had a 
temperature given to it far higher than that necessary to produce the great magnetic 
change in the metal itself (2346.). 
2351. The oxide of cobalt also was magnetic, and equally magnetic whether hot 
or cold. Glass coloured blue by cobalt is magnetic in consequence of the presence 
of the oxide of that metal, and is so whether hot or cold. In all these cases the de- 
gree of power retained was very small compared to that of the pure metal. 
2352. Proceeding to the salts of iron, I found them magnetic. Clean crystals of 
the proto-sulphate of iron were attracted and pointed axially very well ; so also did 
the dry salt. As I proceeded I found that every salt and compound containing iron 
in the basic part was magnetic. To enumerate the different substances subjected to 
trial would be tedious, the following are selected as illustrations of the variety in 
kind : — 
Protochloride. 
Perchloride. . 
Iodide. 
Protosulphate. 
Persulphate. 
Protophosphate. 
Perphosphate. 
Nitrate. 
Carbonate. 
Prussian blue. 
2353. Amongst native compounds- 
Bog iron ore. 
Hsematite. 
Chromate of iron. 
Yellow sulphuret of iron. 
Arsenical pyrites. 
Copper pyrites, and many others were magnetic. 
2354. Green bottle-glass is comparatively very magnetic from the iron it contains, 
and cannot be used as tubes to hold other substances. Crown-glass is magnetic 
from the same cause. Flint-glass is not magnetic, but points equatorially. 
2355. Crystals of the yellow ferro-prussiate of potassa were not magnetic, but were 
repelled and set equatorially ; and such was the case also with red ferro-prussiate. 
2356. According to my hopes, even the solutions of the ferruginous salts, whether 
in water or alcohol, were magnetic. A tube filled with a clear solution of proto- or 
persulphate of iron, or proto- or perchloride, or tincture of muriate of iron, was 
attracted by the poles, and pointed very well between them in the axial direction. 
2357. These solutions supply a very important means of advancing magnetical 
investigation, for they present us with the power of making a magnet, which is at 
the same time liquid, transparent, and within certain limits, adjustible to any degree 
* Annales de Chimie, 1827, vol. xxxvi. p. 337. Comptes Rendus, 1845, vol. xx. p. 1708. 
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