The waste effluent liquors of plants engaged in the manufacture of fish meal from fish waste contain glue. The purification of these liquors to make glue involves the separation of salt and diffusible substances from the glue colloid. Simple dialysis using viscose tubing and electro-dialysis using membranes of parchment paper are effective in removing impurities and producing glue of good quality from waste liquors. Both methods can be used on an industrial scale, the dialysis process being the simpler and more efficient.