Dawson's researches on solutions form a contribution to chemical science of great significance and importance. His earlier work was connected in the main with various aspects of chemical equilibria and more particularly with the formation of complex ions. Thus he was able, by means of distribution experiments, to establish the existence of the complex ion (Cu4NH3) + + in ammoniacal copper sulphate solutions. The other group of compounds in which he was interested was the polyiodides. Here, having confirmed Jakowkin's conclusion of the existence of the tri-iodide in aqueous solutions, he extended the observation to organic solvents such as nitrobenzene, in which he showed that, under appropriate conditions, the higher polyiodides KI9, KI7, KIB exist in significant proportions.