By P. J. MOLONEY and D. M. FINDLAY.
(From the Research Division, Connaught Antitoxin Laboratories, University of Toronto, Toronto, Canada.)
(Received for publication, July 17, 1923.)
In the preparation of insulin on a large scale, a problem which is of considerable importance is the concentration of dilute aqueous solutions of the potent material. On account of the expense and loss of potency which result in boiling down such solutions, it seemed desirable to investigate the possibilities of adsorption. It was found that the potent material could be almost completely removed from aqueous solutions by certain materials, such as decolorizing carbons, but attempts to redissolve the insulin from the solid by heating, altering the acidity, using a different solvent, etc., were only partially successful. It was decided to try some reagent which could be used in a finely divided form, and which could be subsequently dissolved. For this purpose certain organic acids, such for example as benzoic and salicylic, suggested themselves on account of their relative insolubility in water and the fineness of division in which they come down when a dissolved salt is treated with an acid.