Harley comments on the pH of distilled water in reference to the article A Stamp Club Checks the pH of Various Papers, stating that the pH of distilled water is 51/2 which would result in misleading tests. Alfred A. Gruber, secretary of the group which did the research in question, responds that unboiled distilled water does have a pH of 51/2 but boiling will remove dissolved carbon dioxide with a resulting pH of 6.9-7. See <i>AATA 17-1131.