A SIMPLIFIED PREPARATION OF SCHWEITZER'S REAGENT ABRAHAM BRESLAUL Alexander Hamilton High School, Brooklyn, New York
THE wide use of the artificial fiber in industry has made the study of this product a "must" even in elementary courses of chemistry or general science. Schools which demonstrate the production of artificial fibers usually use cellulose regenerated from Schweitzer's reagent as the simplest means of showing this phenomenon. The demonstrator merely squirts some of the prepared solution into a dilute solution of sulfuric acid to produce crude cords of cellulose. It is even possible to dissolve the cotton in the solution in front of the class and complete the process within ten minutes. The crude, thick threads thus formed have the advantage of being visible across the room. Unfortunately, Schweitzer's reagent is difficult to prepare and keep, and involves the discomfort of working over concentrated ammonia. Many of the discomforts of the common process may be avoided by using a simple apparatus based upon the work of Sako~tchikoff,~ who used a weak Schweitzer's reagent to swell fibers as an aid in their analysis. Sakostchikoff contributed, among other interesting points, the fact that the dissolving power of the reagent is a function of the Cu ion concentration, and that the ammonia concentration is not important, providing it is above 6 per cent. This is contrary to the common belief that the ammonia concentration must be very high, as much as 28 per cent. m h e operation of the apparatus is simple. Air is bubbled through two bottles of limewater to remove carbon dioxide. It is then bubbled through a tower containing copper metal in 28 per cent ammonia. Schweitzer's reagent, strong enough to be used for the 1 Present address: Corporal A. Breslau, Balloon Barrage School Detachment, Camp Tyson. Tennessee. a SAKOSTCRIKOPP, Milliard Magazine, I, 882 (1929).
demonstration, is formed in about two hours. To remove fumes, the air train may then be run into a weak sulfuric acid solution with a capacity of 500 cc. Ample material for the several demonstrations is provided. The tower is made of very large glass tubing, such as a broken one-liter graduated cylinder. A threeholed stopper in the top carries a long inlet tube reaching to the bottom of the tower, a short outlet tube, and a dropping funnel for filling and washing the tower. A one-holed stopper in the bottom is provided with a glass stopcock for draining. The tower is then filled with copper turnings, gauze, or wire. It is cleaned by rinsing with dilute nitric acid and water without removing the copper, and is put away complete until the next term when i t is similarly cleaned and is ready for use. This method of producing Schweitzer's reagent involves only three short steps, compared with seven lengthy operations for the older process. The resulting reagent has an ammonia concentration of about 15 per cent, which is not irritating to the eyes, yet quite as strong as 28 per cent ammonia in dissolving power. The solution can be run into an Erlenmeyer flask in the classroom without causing trouble. In actual practice a t our school, cotton is dissolved in the solution until the solution is saturated but not too viscous. It is then squirted out of a small wash bottle with a pressure bulb. The receiving solution is a 1:10 solution of sulfuric acid in a flat tray. Cords of cellulose, one-eighth inch thick and from four to twelve inches long, are formed, which decolorize in five minutes. The process is simple to operate, uses a minimum of materials, involves less time and care, gives a less irritating solution, and leaves a cleaner laboratory than the older method of preparing this solution for classroom demonstration.
