The present investigation is preliminary to a study of the mechanisms by which acids and alkalis damage the cornea. Previous work in this field has been relatively devoid of quantitative analysis. We feel that the prerequisites of a rigorous approach to this problem are: (1) the utilization of isotonic solutions of known ph composed of simple acids, alkalis or buffer substances; (2) the separation of the physical factors of penetration from those purely chemical effects in which we are primarily interested, and (3) the elaboration of a numerical method of evaluating the severity of the reaction produced, so as to yield data which may be studied statistically and graphically. METHODS AND MATERIAL Solutions Used. —In order to have a buffer solution with essentially the same molecular composition over the entire range of ph studied, we have used the following solution, which is similar to that described by Teorell