An improved laboratory method for residual linters on cottonseed

T hE A.O.C.S. OFFICIAL METHOD Aa 7-44 is defined as a method to determine the residual lint (cellulose fiber) on the seed and is applicable to cottonseed. I t is an adaptat ion or modification of A.O.C.S. Official Methods Aa 4-38 and Aa 5-38, which were originally developed in the Barrow-Agee Laboratories by C. H. Cox, then chief chemist. The method for lint determination, during a number of years of use, has proved to be reasonably satisfactory and reproducible but does not lend itself well to the making of a large number of lint determinations in a Commercial or plant laboratory within a short period of time. When it seemed probable t h a t the percentage of residual lint on cottonseed af ter completion of the ginning process might be made a factor in the grading of cottonseed u n d e r the supervision of the Agr ieul tural Marketing Service, U. S. Depar tment of Agriculture, there was begun in the Barrow-Agee Laboratories a s tudy of the official method for the purpose of improving or modifying this method, or developing a new o n e which would be more suitable for analyzing a large volume of samples. The basic principles of the official method, that is, hydrolysis by means of heat and moist hydrochloric gas followed by mechanical brushing, were regarded as sound, and efforts were directed to improving the application of these principles. At the beginning of the s tudy at tent ion was directed toward the application of inf rared heat, because of its instantaneous radiation, as a means of replacing the slower convection type heat. Upon evidence of the feasibility of using infrared heat, a program was init iated to determine the variables and the limitations within which those variables could be expected to give accurate and reproducible results. Consideration was given to the time, oven air temperature, and heat intensity, which combines lamp wattage and proximity to the sample. Many variations and combinations of these factors were at tempted before establishing the optimum conditions suitable for the procedure. This phase of the study resulted in the selection of 125-watt lamps placed in opposing directions, each 6 in. from, and focussed to bear direct ly upon the sample. Oven air temperature was maintained at 118 ~ • 3 ~ C. by a thermoregulator. Because of the high transmission factor of glass toward infrared rays, heat-resistant glass dishes, 5 in. inside diameter, were selected as the container best suited for drying the sample. This part icular diameter is relatively equivalent to the diameter of the lamp beam and also permits d is t r ibut ion of the sample to a thin depth for direct contact with the infrared rays for uniform drying. I t was noted, earlier in the study, that the l int is more readily hydrolyzed when the moisture in the seed is between 3 % 9 % at the beginning of the fuming phase. This fact tends to eliminate the necessity for dry ing low moisture seed. However the imprac-