ON THE PURIFICATION OF SODIUM CELLULOSE XANTHATE.

Abstract

In this paper the purifying methods of sodium cellulose xanthate from viscose were studied with the objects of investigating (1) the minimum decomposition of xanthate, (2) the rapid and uniform purification, and (3) the easy handling of large quantity of viscose.Following reagents were used for the purification. (1) methanol, (2) absolute alcohol, (3) saturated sodium chloride solution, (4) absolute alcohol and saturated sodium chloride solution, (5) absolute alcohol and acetic acid.Results of experiments.Methods of analysis.Regenerated cellulose. Xanthate was dissolved in dilute solution of caustic soda, and the cellulose was regenerated by the addition of dilute hydrochloric acid.Sulphur. Xanthate, dissolved in dilute caustic soda solution, was oxidised with bromine water and the sulphur was determined as barium sulphate.Sodium. The ashes of xanthate were heated with a few drops of sulphuric acid and the sodium was determined as sodium sulphate.(1) Purification by methanol.As methanol decomposes xanthate, the process must be carried out with great care. The analytical results of xanthate by this method have shown lower contents of sulphur and sodium in comparison with those by alcohol and acetic acid method.(2) Purification by absolute alcohol.Xanthate is decomposed a little by absolute alcohol but it is very difficult to remove all impurities by washing with alcohol. This method gives higher contents of sulphur and sodium due to residual impurities, and if the xanthate is washed by methanol, the analytical results become similar to those of methanol method.(3) Purification by saturated sodium chloride solution.It is very difficult to salt out xanthate from fresh crude viscose by saturated sodium chloride solution. By this method, a light green xanthate is obtained, but it contains much sodium chloride which is very difficult to remove.(4) Purification by alcohol and saturated sodium chloride solution. The xanthate was precipitated by the dehydration with absolute alcohol from fresh viscose which is in unstable state with the addition of saturated sodium chloride solution, but it contained fine crystals of salt and their separation was very difficult.(5) Purification by alcohol and acetic acid.Dilute acetic acid (about 1N) is carefully added to the viscose using phenolphthalein as an indicator, when the red color nearly disappear, absolute alcohol is added immediately, and the xanthate is precipitated by dehydration. The whole process must be carried out very quickly and skillfully. This method is very easy to handle a large quantity of viscose. The xanthate thus obtained is washed with absolute alcohol several times, then with ether and dried in vacuum desiccator. The solubility in water is very good and the color is nearly white.(6) The xanthate (Na; 9.9%, S; 7.3%) was steeped in (a) acetone, (b) methanol and (c) absolute alcohol respectivelyf or 117 hours at room temperature, and then analysed, the results were as follows.Na% S% Solubility in water.(a) 10.0 7.3 good(b) 5.0 4.4 bad(c) 8.3 6.0 poorThese results show that methanol affects the xanthate.(7) The authors have obtained the best results with absolute alcohol and (c) acetic acid method. The xanthate purified by this method is of high purity and has good solubility in water.The report concerning to the properties of xanthate purified by this method will appear later.