The number of investigations of the exact acidity, that is, the hydrogen ion concentration, of infants' stools reported in the literature are comparatively few. When the possible importance of the relation of the acidity of the stools to the general condition of the infant, the rate of growth, the presence of fermentative diarrhea, parenteral infections and many other conditions are considered, it is rather surprising that so few determinations have been reported. The only results which we have been able to find have been recorded in the German literature.
The earliest reported figures on the pH of infants' stools are those recorded by Eitel1 in 1917. He found that stools from breast fed infants usually had an acidity of pH from 4.6 to 5.6, although many values were obtained outside these limits. Stools from infants fed on cows' milk dilutions in the majority of cases gave values
TISDALL FF, BROWN A. STUDIES ON THE ACIDITY (HYDROGEN ION CONCENTRATION) OF INFANTS' STOOLS. Am J Dis Child. 1924;27(4):312-331. doi:10.1001/archpedi.1924.01920100017003