Percentage. of Free: Acid Percentage of freeacid 
512 Proceedings of Royal Society of Edinburgh. [sess. 
It appears that the calculated results are too low when the 
amount of free acid in the solution is higher than about 80 per 
Fig. 2. 
lent., and too high wnen the percentage is less than this. The 
second series certainly does not exhibit this feature in the same 
Fig. 3. 
regular way as the other two, the agreement between the two 
curves being particularly good with the exception of one point 
