280 F.. W. Clarke—Todates of Cobalt and Nickel. 
Art. XXX VIIT.— On the Lodates of Cobalt and Nickel ; some Spe- 
cific Gravity determinations; and an Analysis of Sylvanite 
om Colorado; by F. W. CLARKE, Professor of Physics and 
Chemistry. Numbers IV, V, and VI, of Laboratory Notes, 
from the University of Cincinnati. 
IV. On the Lodates of Cobalt and Nickel. 
Axovt forty years ago Rammelsberg described the iodates 
of cobalt and nickel.* He dissolved the freshly precipitated 
carbonates of the metals in an aqueous solution of iodic acid, 
and, upon concentrating, obtained the salts in the form of crys- 
talline crusts. To the cobalt salt he assigned a quantity of 
water of crystallization represented by 14 molecules, while the 
nickel iodate was found to be monohydrated. 
During the winter of 1876-1877 I put one of my laboratory 
students, Mr. H. B. Fullerton, at work upon the iodates, requir- 
ing him, among other salts, to prepare the two in question. 
Rammelsberg’s mode of preparation was followed, and results 
somewhat different from fie obtained. 
hen cobalt carbonate is dissolved in aqueous iodic acid 
and the filtered solution evaporated rapidly over a flame, Ram- 
melsberg’s iodate readily separates out, nearly the whole of the 
salt being deposited in a very few moments. But when, on 
the other hand, the solution is allowed to evaporate spontane- 
ously, small red crystals are formed, having the composition 
Co his is evidently the normal iodate, since it con- 
tains the same number of molecules of water as are found in 
the chlorate, bromate, nitrate, chloride, bromide, iodide, hypo- 
phosphite, hyposulphite, dithionate, selenate, and numerous 
other salts. Indeed, a large majority of the known salts not 
only of cobalt and nickel, but also of zinc and magnesium, 
crystallize with six molecules of water. So general does this 
rule appear to be that all exceptions to it ought to receive the 
most careful scrutiny. Even the sulphates of these metals, 
&. are well known to be 
