THE PRECIPITATION OF COLLOIDS BY MEANS OF ALUMINIUM HYDROXIDE

John. Marshall, William H. Welker
1913 Journal of the American Chemical Society  
It has long been common knowledge among chemists that when precipitation of aluminium hydroxide is induced in solutions, or when freshly precipitated aluminium hydroxide is added to solutions containing substances in suspension, and also t? liquids containing various substances in solution, these substances are carried down in association with the aluminium hydroxide. Because of this property it is used in industrial chemistry to clarify liquids and to precipitate organic coloring matters. The
more » ... oring matters. The mordanting property of aluminium salts in the process of dyeing may be attributed to the action of aluminium hydroxide produced in the process. It also comes into use in mechanical water filters, in sugar analysis and in water analysis as a clarifying and decolorizing agent. This investigation was undertaken with the view of determining whether aluminium hydroxide had wide application as a precipitating agent in respect to inorganic and organic colloids. While there are many references in literature respecting the behavior of aluminium hydroxide as a precipitant of various substances, Rohland' is the only investigator who apparently has taken up the question of the behavior of aluminium hydroxide as a precipitant of colloids. This investigator, while briefly stating that aluminium hydroxide among other hydroxides precipitates certain colloids, confines his investigations largely to the behavior of clays on colloidal solutions. The aluminium hydroxide used in our experiments was prepared by precipitating it with dilute ammonium hydroxide from dilute solutions of ammonium alum contained in large glass cylinders. The ammonium hydroxide was slowly added with constant stirring of the solution with a glass rod until finally the liquid yielded a faint odor of ammonia. The precipitate was allowed to subside and was washed several times by decantation with distilled water. It was then collected on a filter and washed several times until the filtrate was fairly free from salts and then transferred to a glass cylinder and again washed by decantation until
doi:10.1021/ja02195a022 fatcat:uvwhq3tclnhw3izwrll72pquu4