The Organic Acid Content of Various Samples of Raw Cotton Fiber in Relation to Ash Alkalinity and Leaching by Rain

Abstract

Citric acid, l-malic acid, and total organic acids were detd. by the methods of Pucher, Wakeman and Vickery (1941; 1945) after fuming the samples with HC1 and extracting with ethyl ether. Pectic acid was detd. by the method of Whistler, Martin and Harris (1940). The methods of Fargher and Probert (1926) were used to detn. ash and ash alkalinity. Moisture values were detd. by drying for 5 hrs. at 105 C. The pH of water extracts was detd. by adding 5 ml. of hot water to 0.5 g. of ground cotton fiber, mixing, heating in a water bath for 1 hr., cooling, and measuring the pH with a glass electrode. The raw cotton fiber was found to vary greatly in organic acid contents. The greatest variation was shown by l-malic acid. Some of the same vars., grown at different times or in different places, showed large differences in organic acid content. There was rough correlation between the content of organic acids and the ash and ash alkalinity. Rain and other weathering factors had a profound effect on the organic content of raw cotton fiber, especially on the l-malic acid content.