Intelligence and Miscellaneous Articles, 79 
The negative magnetic rotatory power of the salts of peroxide of 
iron is much greater than that of the protosalts. An aqueous solution 
of perchloride of iron containing 40 per cent. of salt, exerts a negative 
action upon polarized light six or seven times greater than the 
action of water, and nearly equal to that of Faraday’s heavy glass. 
fétherial and alcoholic solutions give the same results. But wood- 
spirit appears to be the most suitable solvent; it can take up a 
considerable quantity of iron-salt, remaining much more transparent 
than water, zther or alcohol with a similar quantity of salt. By 
dissolving 55 parts of perchloride of iron in 45 parts of wood-spirit, 
a liquid is obtained, which, from its transparency, is adapted for exact 
observations, and the action of which upon polarized light is nearly 
double that of heavy glass, but in the opposite direction. The 
author made use of this liquid to see whether the magnetic rotatory 
power of the salts of iron varied according to the same laws as that 
of ordinary transparent substances. He compared the rotation 
produced by 1 centim. of the solution, with the opposite rotation of 
the same thickness of sulphuret of carbon, and caused the amount of 
the rotation to vary, by altering the intensity of the electro-magnet, 
the size and form of the armatures, or their distance from the trans- 
parent substance. ‘The proportion of the two rotations was always 
the same, so that the negative rotation produced by the salts of iron 
varies in accordance with the same laws as the positive rotation 
caused by transparent substances in general. 
From the experiments of Plicker and Faraday, it is known that 
the ferrocyanide of potassium is diamagnetic, and the ferridcyanide 
slightly magnetic. The author found that the rotatory power of 
the ferrocyanide is positive and pretty considerabie; that of the 
ferridcyanide negative and very great. 15 parts of ferridcyanide, 
dissolved in 85 parts of water, furnish a liquid the rotatory power of 
which is twice as great as that of water. 
Nickel.—All the salts of nickel have a positive rotatory power, so 
that their solutions exert a greater action upon polarized light than 
that of the water which they contain. This positive rotatory power 
is well marked, and comparable to that of the salts of zinc and tin. 
Cobalt.—The magnetic rotatory power of the salts of cobalt is 
positive, but weaker than that of the salts of nickel. It is rather 
difficult to be shown, as no salt of cobalt can be dissolved in con- 
siderable quantity in water without diminishing the transparency 
of the liquid. 
Manganese.—The protosalts of manganese possess a positive 
and anhydrous sulphate, the phenomena observed could be represented 
numerically, by attributing to the water and the anhydrous sulphate con- 
trary actions proportionate to the density which these two bodies possess in 
the solution. On the other hand, this was impossible, supposing the 
solutions to contain water and crystallized sulphate of iron with 7 atoms 
of water. Hence it appears probable that the dissolved salt is not the 
erystallized, but the anhydrous sulphate; and the same kind of experiment 
may perhaps be applied to the solution of some analogous chemical 
questions. 
