The yield and the purity of glycine obtained after ammonolysis of monochloracetic acid with hexamethylenetetramine followed by a crystallization in a hydromethanolic medium depend on the fraction of methanol in the mixture. Influence of the solvent composition on the solubility of a restored reaction mixture as a function of temperature was first studied for diverse methanol weight fractions in the medium. The results showed that the best conditions for crystallization should be located in a 70-100% methanol weight fraction range with a temperature lower than 10 degrees C. These conditions were then optimized by the golden section search. The results obtained confirmed previous trials and indicated that the optimal methanol weight fraction is 80%. In these conditions, the yield of pure glycine obtained by crystallization was about 92.3% (for a final temperature of 7 degrees C) and the crystals were 98% pure.