242 Proceedings of Roycd Society of Edinburgh. [sess. 
Here it is evident that both the iodine which is chemically trans- 
formed and the iodine which is absorbed, fall off with the amount 
of iodine originally present, but in no case is the iodine wholly 
destroyed as such ; and although the iodine in the magnesia of the 
first experiment is greater in amount than the iodine originally 
taken in the fourth experiment, yet in the latter case some of the 
iodine remains unabsorbed. It would appear, therefore, from a con- 
sideration of these numbers, that there is an equilibrium between 
the iodine remaining in the solution and the iodine absorbed by the 
magnesia, in accordance with the results of the extraction experi- 
ments previously referred to. 
The only difference between the following set of experiments 
and the foregoing is that the magnesia, instead of being precipitated 
before the addition of the iodine, was precipitated in presence of 
the iodine. It was hoped that in this way the magnesia in 
process of formation from magnesium sulphate and caustic soda 
would at once saturate itself with iodine ; and also that the amount 
of iodine chemically transformed would be reduced. The solution 
was in each case filtered one minute after the addition of the 
caustic soda. 
Volume. 
Iodine taken. 
Iodine 
remaining. 
1 2 in lOMgO. 
Iodine 
transformed. 
30 c.c. 
2-50 
0-132 
1-92 
0-54 
3 5 
2*00 
0-039 
1-63 
0*39 
3 3 
1*50 
0-035 
1-24 
0*25 
3 3 
1-00 
0*025 
0-80 
0-19 
Our expectations were to some extent fulfilled, as the amount of 
iodine absorbed was in each case greater than in the former series, 
and the amount chemically transformed in each case less. On the 
whole, however, the general aspect of the table remains unchanged. 
An experiment in which the filtration was delayed for fifteen 
minutes after the addition of the soda resulted as follows 
Volume. 
Iodine Iodine I in M"0 Iodine 
taken. remaining. 2 ° ' transformed. 
30 c.c. 2*5 0*077 1*84 0'69 
These figures show that continued agitation increases the amount 
