314 Proceedings of the Royal Society of Edinburgh. [Sess. 
iodine mark the number of iodide ions present in the saturated solution, 
and join these two points by a straight line. The intermediate values will 
be found to lie along this line, not departing from it more than can be 
accounted for by the experimental error. 
Dawson has shown that the ionisation of KI 3 is the same as the ionisa- 
tion of KI, so that if we consider the ratio of combined to uncombined K 
ions, it is evident that the un-ionised K ions will remain constant, and will 
be represented in the diagram by a perpendicular line ab, drawn from *79 
Iodine Ions against total Iodine in normal KI 
Graph 5. 
on the base line, while the distribution of the K ions between I and 
I., ions is given by the line a c for any given amount of iodine in 
solution. It appears further, from a consideration of this graph, that 
KI 3 is practically the only complex present. For if we consider the 
solution containing *5 molecules of iodine, we find that the number of free 
iodine ions present is '41, which means that the amount of free KI present 
is just about *5, thus leaving ‘5 of KI molecules combined with the 5 iodine 
molecules as KL. If, on adding more iodine to this solution higher com- 
plexes were formed, the graph would not continue as a straight line. 
If we consider again the table in Jakowkin’s paper for normal KI, it 
