Calcium Hypochlorite Solutions: Evaluation of Surface Tension and Effect of Different Storage Conditions and Time Periods over pH and Available Chlorine Content

Introduction: The aim of this study was to evaluate the pH and the available chlorine content from sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca[OCl]2) solutions stored in different conditions and time periods and the surface tension of Ca(OCl)2 solutions in comparison with NaOCl.. Methods: Solutions at 0.5%, 1%, 2.5%, and 5.25% concentrations were prepared. The pH level and the available chlorine content of freshly prepared solutions and solutions stored for 30, 60, and 90 days at 25 degrees C, 4 degrees C, or 37 degrees C were evaluated in a digital pH meter and by titration, respectively. Surface tension was tested using a Du Nouy tensiometer (Sigma 702, Force Tensiometer; Attension, Espoo, Finland). Descriptive and inferential statistical analyses were performed. Results: A precipitate formed by 2.5% and 5.25% Ca(OCl)(2) solutions was observed. Ca(OCl)(2) showed a higher concentration of available chlorine than NaOCl. Both 2.5% and 5.25% NaOCI and Ca(OCl)(2) had a decrease in the available chlorine content when compared with freshly prepared solutions; 0.5% and 1% NaOCI tend to have a lower pH compared with 0.5% and 1% Ca(OCl)(2). NaOCl, 5.25%, showed higher pH compared with 5.25% Ca(OCl)(2). NaOCI and Ca(OCl)(2) in 0.5% and 1% concentrations tend to show a reduced pH level, whereas 2.5% and 5.25% solutions showed an increase in pH. The heat contributed to the instability of the solutions. NaOCI showed lower surface tension values than Ca(OCl)(2). Conclusions: Ca(OCl)(2) solutions are extremely alkaline and tend to have more available chlorine content than NaOCl but have a higher surface tension than NaOCl. Regarding the available chlorine content, these solutions tend to be stable to 30 days of storage when kept at 4 degrees C or at 25 degrees C.