A Simple Classroom Demonstration of the Manufacture of Rayon F. FROMM Polytechnic Institute o f Puerto Rieo, San Germin, Puerto Rieo
DEMONSTRATION of the production of THE rayon is rendered considerably more effective if not only the use of Schweitzer's reagent and the reprecipitation of cellulose is shown ( I ) , but if thread is actually produced. In contrast to the common belief, neither complicated machinery which needs several hours of preparation nor a t least one assistant for the performance (Z), are necessary. The lecturer may manage the whole process easily alone if the equipment shown in Figure 1 is used. The essential part of the apparatus is a glass tubing six mm. wide, which is bent rectangularly and is stretched a t one end so as to form a nozzle, one-half to one-tenth mm. wide. The glass tubing is connected to a small separatory funnel by means of a short rubber tubing and a screw clamp Funnel and tubing are filled with the cellulose solution. The screw clamp is adjusted so that five to 15 drops of solution leave the nozzle per minute. The nozzle is placed in a photographic tray, 10 to 15 cm. long and filled with the precipitating bath. The thread will be formed quicker and will be much stronger if concentrated sodium hydroxide (approximately 30%) is used for precipitation. As soon as the first drop of cellulose solution enters the precipitating bath, i t is taken by forceps and is carried gently through the whole length of the bath to a glass tubing (1.5 to 3 cm. wide) which turns around an axle and can be suitably constructed of a broken test tube, two cork stoppers and pieces of an "Erector" set. If this primitive bobbin is turned slowly by hand, up to 30 yards of thread can easily be produced. Care should be taken that the parts of the thread do not cross each other on the bobbin but are placed side by side. The raw thread still contains all the copper. It is decolorized by a short treatment with five per cent acetic acid. The fiber is then washed for 24 hours by placing it on the bobbin in a beaker with water and is eventually dried. A fairly strong fiber is obtained though, of course, the tensile strength of the commercial product cannot be reached.
The same equipment can also be used for viscose solutions, if sulfuric acid is applied for precipitation, but the fibers obtained are weak and much less satisfactory.
LITERATURE CITED
(1) BRESLAU, THIS JOURNAL, 19, 356 (1942). (2) JENKINS, GABUZDA, AND SAUER, ibid., 18,433-1 (1941)
