INDUSTRIAL Ah’D ENGINEERING CHEMISTRY
May, 1928
The Copper Number Test
Although the determination of the Schwalbe copper number of oxidized cellulose has been employed as a measure of the degree of attack, the method has recently been subjected to considerable criticism on account of its empirical nature.” Hydrocellulose also possesses the property of reducing Fehling’s solution. These cellulose degradation substances can not be differentiated by either the copper number test or the alkali solubility determination. Ristenpart18 discovered that the determination of copper numbers of dyed cotton is complicated by the fact that most dyestuffs fix a certain amount of copper. To correct for this retention of copper a blank test must be made on cotton free from oxidized cellulose but dyed to match the colored sample. Apparently, Ristenpart has overlooked the possibility of using the SchwalbeHagglund copper number procedure in which only the copper in the cuprous state is determined. The volumetric method of Schwalbe and Becker for estimating the acidity of oxidized cellulose has been investigated by Karrer and LieserI8who found that all such preparations, when titrated with phenolphthalein as the indicator, consume small amounts of alkali. The figures obtained do not parallel the copper number, which is to be expected. Acidity is expressed in the form of the “acid number,” which is the number of cubic centimeters of normal solution required to titrate 1 gram of oxidized cellulose using the above indicator. A recently developed procedure which is claimed to be superior to the Schwalbe copper number is based on the reaction of a sodium acetate solution of silver nitrate with the aldehydic groups in the cellulose product.lQ The amount of silver separated on the fibers is quantitatively determined by dissolving the metal in nitric acid and titrating the resulting solution with 0.01 N ammonium thiocyanate solution. A second treatment is necessary on the same fibers to determine the silver retained by adsorption. I n their published researches on the chemical analysis of cotton, Birtwell, Clibbens, and GeakeZ0announce that the rise of the copper number relative to the fall of viscosity of hydrocellulose preparations conforms to a simple equation, NcuVz = 2.6, where NcU is the copper number and V is the log of the relative viscosity of the cuprammonium solution. By this means i t is possible to differentiate sharply between hydrocellulose and oxidized cellulose. Improved methods for the analysis of cotton materials, developed a t the Shirley Institute, England, consist chiefly of the SchwalbeBraidy copper number test, viscosity in cuprammonium solution, and methylene blue absorption from buffered solutions. Using these methods the rates of consumption of oxygen by cotton cellulose and changes of its properties were
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investigated. Within the range of hydrogen-ion concentration p H 5-10, characteristic of commercial hypochlorite bleach liquors, the maximum rate of attack on the cellulose occurs a t the neutral points6 Slightly acid hypochlorite solutions are less rapid in their action than neutral solutions. In a strongly alkaline solut,ion hypobromite is a more rapid oxidizing agent. For a constant oxygen consumption alkaline hypochlorite solutions produce the lowest copper numbers and highest methylene blue absorptions; acid solutions produce the highest copper numbers and lowest absorptions; the neutral solutions are intermediate in both respects. For a constant time of t,reatment the neutral solution yields higher copper numbers and methylene blue absorptions than either slightly acid or alkaline liquors.’ The most common cause of overbleaching in industrial practice is evidently the excessiye use of hypochlorite solutions in the vicinity of the neutral point. Conclusion
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In agreement with Cross and DorBeI2’a review of the literature on cellulose degradation products leads to the critical and inevitable conclusion that there are no lines of demarcation or differentiation justifying the term “oxycellulose” as applied to a chemical individual. To prevent ambiguity the term “oxidized cellulose” is much to be preferred to denote suc,h a mixture of reactions which evidently are involved in the oxidation of cellulose. Bibliography 1-Weiser, Colloid Symposium Monograph, Vol. IV, p. 174 (1926). 2-Karrer, “Polymere Kohlenhydrate,” p. 198 (1925). 3-Knecht and Mueller, J . SOC.Dyers Colouristr, 42, 46 (1926); PapierFabr., 24, 476 (1926). 4-Knecht and Egan, J. Soc. Dyers Colourisfs,39, 67 (1923). 5-Clibbens and Ridge, J. Textile I n s f . , 18, 135T (1927). 6-Heuser, Papier-Fabr., 25, 241 (1927). 7-Birtwell, Clibbens, and Ridge, J . Textile Insf., 16, 13T (1925). 8-Karrer and Lieser, Cellulosechemie, 6, 2 (1926). 9-Hibbert and Parsons, J. Soc. Chem. Ind.,44, 473T (1925). 10-Heuser and Niethammer, Cellulosefhemie,6, 13 (1925). 11-Herzog, Papier-Fabr., 23, 121 (1925). 12--0tt, Helu. Chim. Acto, 9, 31 (1926). 13-Schwalbe and Feldtmann, Ber.. 58, 1534 (1925). l4-Marcusson, 2. angew. Chem., 99, 898 (1926). I F A t s u k i , J. Faculty Eng. Tokyo I m p . Uniu., 15, 55 (1924); C. .A , 19, 727 (1925). 16-Hess, Papier-Pabr., 23, 122, 164 (1925). 17-Clibbens and Geake, J . Textile Inst., 16, 27T (1924); Papier-Fabr., 25, 401 (1927); Staud and Gray, IND.ENG. CHBM.,17, 741 (1925); 19, 854 (1927); Schwalbe, Papiev-Fabr., 25, 157 (1927). 18-Ristenpart, Melliands’ Texlilber., 6, 830 (1925). Ig-Anon, 2. angew. Chem., 39, 343 (1926); Papiev-Fabr., 24, 492 (1926). 20-Birtwel1, Clibbens, and Geake, J . Textile Inst., 17, 145T (1926). 21-Cross and Doree, “Researches on Cellulose,” Vol. IV (1922).
Purification of Alcohol for Preparation of Alcoholic Potassium Hydroxide1 Sol Kiczales 1956 CROTONA P A R K W A BRONX, Y, New YORK,N. Y.
P R E P A R E a solution of lead acetate containing 2.5 to 3 grams of lead acetate in 5 ml. of distilled water for each liter of alcohol. Add the solution to the alcohol in a glassstoppered bottle and thoroughly mix. Dissolve 5 grams of KOH in 25 ml. of warm alcohol (for each liter of alcohol), cool the solution somewhat and pour it slowly, without stirring, into the alcoholic solution of lead acetate. After one 1
Received F e b r u a r y IO, 1928
hour, shake thoroughly. Let the mixture stand overnight or until most of the precipitate has settled, filter and distil. The precipitate formed is evidently an addition product of lead oxide and the aldehyde, formed by a reaction similar to that between silver oxide and aldehyde. This method is better than the silver oxide method, not only because of its economy, but also because the lead oxide-aldehyde product is more insoluble than the silver oxide-aldehyde product, and therefore the removal is more complete.
