LITERATURE CITED i. 2. 3.
4. 5. 6.
B. V. loffe, Refractometric Methods in Chemistry [in Russian], Khimlya, Moscow (1974), ~p. 256-283. ~. A. Nemchenko, I. A. Novikov, S. A. Nevakova, et el., Propertles of Man-Made Fibers and Methods of Determining Them [in Russian], Khimiya, Moscow (1973). V. E. Moskaleva, Z. E. Bryantseva, E. V. Goncharova, et al,, DiaEnostic Principles of Nonwoody Plants and Man-Made Fibers [in Russian], N, P. Zolotova-Spasska, ed., Lesnaya Promst., Moscow (1981). A. F. Forziati, in: Analytical Chemistry of Polymers, G. Klein, ed., [Russian translation], Mir, Moscow (1965), Vol. 2, pp. 95-114. R. Meredith and J. Hearle, Physical Methods of Investigat!ng Textiles [Russian translation], Gislegprom, Moscow (1963). M. Born and E. Wolf, Principles of Optics, Pergamon (1970).
AN IMPROVEMENT IN THE METHOD OF DETERMINING THE FREE CAUSTIC SODA CONTENT OF VISCOSE O. N. Bobrova, É. I. Meskina, T. B. Filicheva, E. V. Yakanina, and Z. S. Lapkina
UDC 677.463.021.123.014.23
The free caustic soda content of viscoseis one of the very important indices which affect the properties of the viscose and its suitability for spinning [I, 2]. In connection with the fact that the existing methods of determlning the free caustic soda content ere inaccurate, a calculational method of determining it has been proposed [2], based on analytical data on the total alkali content of the viscose, the content of cellulose xanthate, of sodium trithiocarbonate, and the degree of solvation on the cellulose hydroxyl groups. The lack of agreement between the calculated figures and the results of ena!ytical determination by titration [3, p. 137] is explained, in addition to the reasons enumerated in [2], by the possibility of additional bind of caustic soda by carbon disulfide, llberated as a result of the reactions NazCS,~- 2Ks[Fe(CN),] 3CS,+6NaOH
(i)
* S ~-2K,Na[Fe(CN),]~-CS2 » Ne,eS3+ NatO, + SH,O
(2)
To prevent tying up of caustic soda by the liberated carbon disulfide and to speed up the analysis, we have eliminated the operations of preliminary precipitation of the cellulose xanthate by a saturated sodium chloride solution and oxidation of the sulfur-containing impurities in the viscose by potassium ferricyanide. It is well known [4, p. 224, p. 293; 5, p. 303] that cellulose xanthate, sodium carbonate, and sodium sulfite form precipitates with exces$ barlum chloride which are insoluble in an alkaline or neutral medium. As out studles showed, sodium trithiocarbonate synthesized from sodium sulfide and carbon disulfide alsoforms a precipitate of barium trithiocarbonate, which is titrated at pH 4-5. Consequently, in the titration of vlscose in the presence of phenolphthalein (color change fange, pH 8-I0), the free alkali is titrated plus half of the sodium sulfide, whose content in the viscose is slight. The following procedure is recommended for determining the free sodium hydroxide content of viscose. A 0.3-0.5 g sample of viscose, weighed with an accuracy of 0.0002 g by difference in weight of a weighing bottle, is introduced into a conical flask having a capacity of 100 ml, into which 20 ml of distilled watet has preliminarily been poured, and the mixture is
Translated from Khimicheskie Volokna, No. 4, p. 59, July-August, 1983. article submitted October 18, 1982.
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TABLE i. Results of Determining the Free Caustic Soda Content of Viscose by Various Methods Site of sam-lin- I
Composifion of vbco$e, % by Wto
~'1 0ellulose 7 ---NaO H
~
Content of free NaOH, °B by w't. recommen[ ed method
After solution From spinning machine
After ripening under laboratory conditions for ind/cated time
periods Oh 16 h 24h
30 h 48 h 54 h
method calculation of [3] method [2]
4,00 4,16 3,28 3,52 3,68 3,78 3,40 3,60 3,58 2,72
4,37 4,62 3,80 4,31 4,28 4,32 4,30 4,49 4,57 3,69
4,12 3,96 3,76 3,64 3,20 3,08
4,54 4,53 4,45 4,43 4,40 4,39
stirred with a glass tod until complete solution occurs. Then 5 ml of a 10% barium chloride is added and the mixture is titrated with a 0.i N solution of hydrochloric acid, using phenolphthalein as indicator. The results of determining free alkällcontent by the method described were compared with the results of determinations by the method of [3], and also with the figures obtained by the calculational method of [2]. We investigated viscose samples during the ripenlng process under laboratory conditions and also investigated a number of specimens of production Viscose. As is evident from Table I, the results of the method described are close to the calculated figures, even though somewhat less than they are, which may be explained by the reasons given in [2]. It should be noted that the free alkali content obtained either by the calculational method or by the presently suggested one are reduced slightly during the viscose ripening process (by 0.2-0.3%), while by the previously used method this reduction amounted to I%. Apparently this is explained by the error of the procedure of [3], since with increase in sodium trichiocarbonate content of the ripened viscoses, libaration of carbon disulfide by reaction (1) increases as we11 as binding of the free sodium hydroxide. • The expendlture of time in determining the free sodium hydroxide content of a viscose by the recommended method is 20 min (by the method of [3], 2 to 3 h). The reproducibility of the results is characterized by a mean-square deviatlon of ±0.07; the coefficient of variation is 2%. CONCLUSIONS In the a=celerated method of determlnlng the free alkali content of vlscose, the operations of separatlng the cellulose xanthate and of oxidlzlng the sulfur-contalning impurlties with potassium ferricyanide are elimlnated. Results from determlnations by the accelerated method essentially coincide with the data obtained by calculation. LITERATURE CITED io
2. 3.
320
T. B. Filicheva, E. M. Mogilevskii, and S. P. Papkov, Khim. Volokna, No. 2, 18 (1974). T. B. Filicheva, Z. S. Lapkina, and A. B. Pakshver, Khim. Volokna, No. 5, 69 (1976). A. B. Pakshver and A. A. Konkin (edltors), Control in the Manufacture of Man-Made Fibers [in Russian],Khimiya, Moscow (1967).
4. 5.
B. V. Nekrasov, Textbook of General Chemistry [in Russlan], Khlmlya, Moscow (1981). Z. A. Rogovin~ Bases of the Chemlstry and Technology of Man-Made Fibers [in Russian], Vol. i, Khimiya, Moscow (1964).
METHODS OF INVESTIGATING THE PHOTOOXIDATIVE DEGRADATION OF CELLULOSE TRIACETATE FIBERS I. S. Polikarpov and G. I. Kotlyar
lYl)C 67.7.464.1:543.253
During the process of photochemical degradation of cellulose triacetate, destruction of the macromolecules takes place, plus formation of compounds whlchcontain peroxy groups, and aldehyde and carboxyl groups. Since these products are reduced at the dropping mercury electrode [1, p. 158], an attempt was made to investlgate the kinetics of buildup of cellulose triacetate degradation products, i.e., the mechanlsm and kinetics of the cellulose triacetate fabric degradation, by polarography methods. Uslng polarography, we tried to determine quantitatively the aldehyde and carboxyl group content by an Indlrect method, using the reaction of aldehyde groups with copper oxide and that of the carboxyl groups with methylene blue. We studied bleached triacetate fabric having a weight of 192 g/m 2, a denslty along the warp of 214 and along the fi11 of 133, prepared by weaving from ordlnary yarnhavlng a linear density of 60 tex. The fabric was irradlated wlth a mercury-quartz lamp for 0.Sj I, 2, 4» or 12 h. The breaking characteristics of strlps of fabric 25 × 100 mm were determlned on an RT-250 breaking machlne whose guaranteed error was in the fange of 2-3%. Polarography was carried out by the procedure of [2]. Two waves are formed wlth half-ware potentlals E2/2 = --1.3 V and EI/2 =--1.7 V relative to the mercury anode. The first ware corresponds to reduction of peroxy compounds; the second, to reductlon of compounds contalnlng aldehyde groups [1, p. 147]. A confirmation of this is the increase in these waves on addition of depolarlzers which are close in chemlcal nature to the solution --hydrogen peroxide or acetaldehyde [3]. For quantitatlve determinatlon of the aldehyde groups we used the reactlon with copper oxide, which is used to determlne copper numbers in cellulose [4, p. 49]; we modlfled it somewhat, the copper content was determlned polar0graphlcally, whlch is signlflcantly more accurate and slmpler. Fabrlc samples of each speclmen were covered with i0 ml of the solution [4~ p, 48], heated in a boiling watet bath for 1 h, cooled» and a polarogram of the solution was taken. Copper content was determlned by a standard method, The dlfference in copper concentration before and after boiling the solution wlth the fabric corresponds to the amount of bound aldehyde groups. Results obtalned, recalculated to m/lllequivalents per gram of fabric» are given in Table 1. Analogously, we determlned the aldehyde group content of fabrlc speclmens after boiling them in a 0.2 N solutlon of llthlum hydroxide~ thatis, in the hlgh-moleeular-welght fractlon of cellulose triacetate. The specimens were washed with watet to complete removal of alkali» dried under conditloned conditions, and investlgated by the procedure described above. For a quantitative determinatlon of the carboxyl groups we used the reactlon with methylene blue [4» p. 301]» which is easily found polar0graphically. Fabric samples (0.2 g) were covered wlth 5 ml of a solutlon containing 0.1 mg/m1 of methylene blue in a 0.I N borax solutlon, and were allowed to s~and for one day at room temperature. Then polargrams of the solutlon were taken. A sharp ware for methylene blue was obtained, with a half-ware potential, EI/2» of --0.3V relative to the mercury anode. By the method of standards we determined the concentratlon of the methylene blue» and then we calculated the amount of bound carboxyl groups, in meq per g of fabrlc. Translated from Khimicheskie Volokna~ No. 4» p. 60» July-August»1983. article submitted October 19, 1982.
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