1896 - 97 .] On the so-called “ Hypoiodite of Magnesium .” 247 
obtained differed considerably from set to set, the general result 
was the same as that indicated in the tables given above. In any 
one set the amount of iodine absorbed by the magnesia diminished 
according as the final concentration of the chloroform solution 
diminished, whether this diminution was due to a smaller quantity 
of iodine, or a greater volume of chloroform being taken. The 
phenomena are therefore much simpler than when aqueous iodine 
is used, the absorption being there complicated by chemical action 
occurring to an equal or even greater extent. 
Taking into consideration both the qualitative and the quanti- 
tative experiments, it is apparent that we are here dealing with a 
case of absorption analogous to the absorption of acids by silk 
(Walker and Appleyard, loc. cit.), and to the absorption of iodine 
by starch to form the blue “ iodide of starch.” The “ hypoiodite ” 
shows no behaviour truly characteristic of a chemical compound, 
unless the extraordinary tenacity with which the iodine clings to 
the magnesia be accounted such. This, however, is not uncommon 
in cases of absorption. It is, for instance, a matter of extreme 
difficulty to remove from charcoal an acid which it has absorbed ; 
and platinum-black behaves with regard to some substances in a 
precisely similar way. 
Kuster (loc, cit.) found that the amount of iodine absorbed by 
starch varied with the concentration of the iodine solution 
employed, though much less rapidly, and this we have found to 
be the case with the absorption of iodine by magnesia. From his 
observations Krister concludes that the blue iodide of starch is 
neither a chemical compound nor a mechanical mixture of iodine 
and starch, but a well-defined solution of iodine in starch. In 
this conclusion he is, in our opinion, scarcely justified, if the word 
“ solution ” is employed in the sense of the “ solid solution ” of 
van’t Hoff. His experiments show that J !(/K vv : K s is constant, 
where K w is the concentration of the aqueous solution, and K s the 
concentration in the starch. Now, were the “ iodide of starch ” a 
solid solution, a necessary deduction from these numbers would be 
that iodine dissolved in water must have a molecular weight ten 
times greater than iodine “ dissolved ” in starch, which is contrary 
to all experience. The same objection holds good against the 
“ solid solution ” theory of dyeing, and against a “ solid solution ” 
