SummarySoybean protein in aqueous alkaline dispersions at pH 10–11 reacts readily with sodium chloroacetate at temperatures of 50–70°C. to give a protein derivative containing 7–9% carboxymethyl groups. Ultracentrifugal measurements indicate no change in molecular size of the protein when the reaction is carried out at 50°C. but lowered molecular weight at 70°C. The reaction with sodium chloroacetate lowers the pH of minimum solubility from pH 4.5–3.1 and renders the protein more soluble at a neutral pH. Dispersions of carboxymethylated proteins exhibit resistance to putrefaction and do not gel on the addition of formaldehyde.