During the investigation of the viscosities of aqueous solutions of tetrapropyl-ammonium chloride, Taylor and Moore noticed that the density of a concentrated solution was less than that of a dilute solution at the same temperature. The following investigation, undertaken at the suggestion of Dr W. W. Taylor, shows how the density depends on the concentration and temperature of the solution.

Tetra-propyl-ammonium chloride was prepared from tetra-propylammonium iodide. Silver chloride was added to an aqueous solution of the iodide and the mixture allowed to stand in the dark for some time. The tetra-propyl-ammonium chloride solution which was formed was then filtered off from the solid silver iodide and evaporated to dryness in a vacuum desiccator. The solid so obtained was a white crystalline substance which was very deliquescent. It was tested and found to be free from iodide.