In the first paper of this series (1) it was concluded as a first approximation that under a standard set of conditions the entire course of the precipitin reaction between the specific polysaccharide of Type III pneumococcus and homologous purified antibody could be quantitatively accounted for by three simple equations. The mass law was believed to hold for these equations, the more so as the reactions were found to be reversible. Studies of the theoretical factors involved have since been continued under more varied conditions, and the present paper describes experiments which have necessitated modification of the conclusions originally drawn.
EXPEI~r&rENTALThe quantitative predpitin determinations were made as in previous papers (2-4), except that the technique was modified as described below in order to study the effect of varying a given set of conditions. In general, precipitates were analyzed, rather than superuatants, as had been done in (I). Much of the serum used was obtained through the kindness of Dr. William H. Park, to whom the writers again wish to express their gratitude. Unless otherwise stated, antibody solutions were prepared according to Felton (6).