1896 - 97 ,] On the so-called cc Hypoiodite of Magnesium?' 245 
at first was fairly rapid, but soon became slower, iodine dis- 
appearing gradually from the solution day after day. In a very 
dilute solution all the iodine apparently passed into the magnesia, 
the chloroform being left absolutely colourless. This pointed to 
no true equilibrium existing under the conditions employed. 
Again, a series of experiments in which the ratio of iodine to 
magnesia was constant, the amount of chloroform alone being 
varied, showed the remarkable result that more iodine disappeared 
from the dilute than from the concentrated solutions. These 
anomalies were evidently due to some chemical action which 
destroyed the iodine, and special precautions were then adopted 
for the removal of moisture from the reacting substances and the 
vessels which contained them. It was found that consistent 
results were obtained only when the magnesia employed had been 
freshly ignited and cooled in a desiccator. The chloroform was 
carefully dried with calcium chloride, kept over sodium, and 
distilled from fresh slices of sodium immediately before use. The 
iodine from which the solutions were made had stood for at least 
several days over strong sulphuric acid in a desiccator, and the 
cylinders employed were dried at 120° in an air oven. As much 
expedition as possible had to be used in weighing off the magnesia, 
otherwise the experiments failed. It was found impracticable to 
weigh off the magnesia and then ignite it just before it was added 
to the iodine solution, for specimens ignited under as nearly as 
possible the same conditions gave very different results, so that no 
comparison between them was possible. To preclude any action 
of light the cylinders containing the solutions were wrapped in 
dark paper throughout the absorption. Even when the above 
precautions were taken to ensure the absence of appreciable 
quantities of moisture, considerable difficulty was experienced in 
obtaining trustworthy results. Preliminary experiments showed 
that after five days the concentration of the iodine solution no 
longer diminished perceptibly, and that continued agitation 
appeared to have very little effect on the time necessary to saturate 
the magnesia. The iodine in the chloroform solution was deter- 
mined by shaking up a known volume with a known volume of 
thiosulphate solution and titrating the excess of the latter with a 
standard solution of iodine. 
