The Variation in the Structure of Water in Ionic Solutions

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Abstract
It has been long thought that the presence of ions in an aqueous solution produces a contraction of the water. Here it is shown by x‐ray diffraction curves (1) that with concentration of ions there is a lessening of the amount of the 4‐coordinated water structure, increasing the density, (2) that the alteration in structure is apparently similar to that produced by increasing the temperature of the water, and (3) that the effect on the water structure is not confined to the shell immediately adjacent to an ion. Further, by the use of fifteen strong electrolytes, selected because of their wide variation in type and also in apparent molal ionic volume, it is shown by measurements on the alteration in the minor diffraction peak (4) that the rate of variation of the liquid structure of the water with ionic concentration has a striking correspondence with the rate of variation of the apparent molal ionic volume. In fact, the alteration in liquid structure seems to have a much more important effect in the apparent molal ionic volume than has an electrostatic theory based on the Debye‐Hückel theory.