PHYSICAL CHEMISTRY OF ENAMEL DISSOLUTION 



245 



formation also depended on the size and shape of the enamel snrface 

 area that was exposed to the decalcification medium. Experimentally, 

 this means that for direct quantitative comparisons, all samples 

 should be of the same size; 15 mm- samples were used throughout 

 the present study. The rate per unit area increased linearly with 



TABLE II. Acid Concentration of Decalcification Medium 

 IN Moles per Liter 



" Calculated and checked by titration. 



'' Determined by titration. The other sample of low buffer content contained un- 

 dissociated acid of 0.026 m at pH 3.5 and 0.022 m at pH 4.5. 



decreasing sample area, approximately doubling for a 50 per cent 

 reduction in surface area (Fig. 39). The effect could be the residt 

 of the greater volume available for diffusion of reactant and reaction 

 products to and from the enamel at the sample edges as compared 

 with the middle of the sample, and, therefore, would be a function 

 of the perimeter of the sample. 



