Rurow's Solution, official in the SATIONAI, FORMULARY as T,iquor Xlumini Acetatis, is prepared by dissolving 150 grams of lead acetate in 500 cc of water, and pouring this in cold solution in a thin stream, with constant stirring, into a cold solution of S.5 grams of aluminum sulphate in 500 ce of water. The mixture is then set aside in a cold place (about 10' C.) for 2-I hours, stirring it occasionally and, finally, making the filtered liquid measure 1000 cc. The quantities of lead acetate and

more »

... aluminum sulphate eniployed are the. result of stoichiometric calculations, the object being to produce a solution containing s(': of aluminum acetate, with practically no lead in the finished preparation. The directions to employ cold solutions and set the mixture aside at a temperature of about 10" C. have for their object the precipitation of lead sulphate, which is formed as a result of the chemical interaction of the lead acetate and aluminum sulphate employed in the preparation of the solution. This procedure is based upon the solubility of lead sulphate in pure water which, according to Seidel, is O.OiLj gram in 1000 cc water a t 1 0 " C. ("Solubility of Inorganic and Orgxnic Compounds," 2nd edition, page :Hi;<.) Being interested in the question of how much lead Burow's Solution, made according to the NATIOSAL I:ORMI:LAKY, should contain, and, having consulted various reference books without finding any other information than that there should be a trace only, I conducted the following experiments. A sample of unertloresced lead acetate, taken from a cork-stoppered bottle, was assayed by tlic C. S. P. method; it showed the presence of 8i.099','; of anhy-.drous lead acetate, which meets the official requirement-"It contains not less than Sj.31 percent nor more than 8937 percent of anhydrous lead acetate." A sample of aluminum sulphate, taken' from a cork-stoppered bottle, when assayed by the method official in the SATIONAI, FORMULARY, showed the presence of 1 6 . 4 5 8~~ aluminum oxide; this fully meets the requirement of the X. F.-"The weight of aluminum oxide is not less than l G . l percent of the weight of aluminum sulphate." Bmploying these chemicals, making all wcighings on an analytical 1)alance with analytical weights, and the final measurements in a glass-stoppered volumetric flask, 200 cc of Burow's Solution were made in strict accordance with the directions of the N. 12. The finished product giving heavy precipitates with all of the commonly employed reagents for lead, thus indicating the presence of more than a trace of the metal, I quantitatively determined the amount by the following methods : A. Five cc of the solution-acidified with slight excess of nitric acid, heated t o boiling and electrolyzed for about 3 hours, 3 volts, l l / z amperes-showed the presence of 0.070 gram of lead as metallic lead per 100 cc. Tcn cc of thc solution, to which a slight excess of sulphuric acid was added, were evaporated down to whitc fumes; 72 cc of cold distilled water were cautiously added, and the solution stirred thoroughly, 25 cc of alcohol were then added, and the solution allowed t o stand over night. The material was then filtcrcd through asbestos on a Gooch crucible; thc prccipitate was washed