The Henry’s law constant defines the solubility of a gas in a liquid solution. In this study, a new method for measuring the Henry’s law constant is described. This new colorimetric method is suited for gases which react with water to form acidic or basic solutions when they dissolve, and makes use of measuring the concentration of two forms of a colorimetric pH indicator. By measuring the concentration of the protonated and deprotonated forms of the indicator with UV-visible absorption spectroscopy, the concentration of the hydronium in solution was determined. After determining the hydronium concentration, the equilibrium expression for the dissolved gas reacting with water was solved to determine the concentration of the dissolved gas. The concentration of the dissolved gas and the measured partial pressure of the dissolved gas at equilibrium were then used to calculate the Henry’s law constant for the gas. The efficacy of the method is demonstrated by measuring the Henry’s law constant for carbon dioxide in water over a range of pressures (0.680 – 5.10 atm). The results obtained with this method are comparable to the value for the Henry’s law constant that have been previously reported via more traditional methods, and yielded values for the Henry’s law constant for carbon dioxide that ranged from 3.45 × 10⁻² to 3.99 × 10⁻² M atm⁻¹.

亨利定律常数定义了气体在液体溶液中的溶解度。在这项研究中，描述了一种测量亨利定律常数的新方法。这种新的比色方法适用于溶解时与水反应形成酸性或碱性溶液的气体，并利用测量两种形式的比色 pH 指示剂的浓度。通过用紫外-可见吸收光谱测量指示剂的质子化和去质子化形式的浓度，确定溶液中水合氢的浓度。确定水合氢浓度后，求解溶解气体与水反应的平衡表达式以确定溶解气体的浓度。然后使用溶解气体的浓度和测量的平衡时溶解气体的分压来计算气体的亨利定律常数。该方法的有效性通过测量一定压力范围（0.680 – 5.10 atm）下水中二氧化碳的亨利定律常数来证明。使用该方法获得的结果与之前通过更传统的方法报告的亨利定律常数的值相当，并且产生的二氧化碳亨利定律常数的值范围为 3.45 × 10 ^-2至 3.99 × 10 ^{- 2}大气压^-1。