Symposium on
.Molecular Weights of Cellulose In the 1-t
1
10 Years sh3dficant advances have heen made in the industzial consideration
and use of cellulose m o l e a h r weight measurementsfor control of cellulose wnvereion proand in evaluation and expression of qualities of the finished pmduota. O ~ a few Y Yearn ago, industrial mea.wmementa of celluloseviacosities were usually exp r e d in terms of the nu& of semnds -ired for a ball of speoified sire to fall thmugh a SpecrSeil height of solution of relatively high concentration. Increments of this expressed viscosity bore only an obscure r e l a t i o d p to the increase or deonase in the basic degree of polymerkation of the cellulose. Today in the industry, w e find growing usage and aceptance of the terms intrinsic viscosity and DP. The wncentration of cellulosein the solution used for viscosity measurement has been greatly d u d , and protective measures used to minimize degradation of the cellulose in the solution have been substantially improved. Yiswdty measurementa are on a much more p~ cise basis, and in m a n y eases such vimwsity measurements have been correlated with independent osmotic or centrifugal measurements to relate them directly to molecular weight.
Along with thisrewgnition of the valueof molecular weight measurements has wme the further realization that a knowledge of the DP level is not enough even for industrial
applications. Cellulose is not a homogenarus material, and in order to adeqmately characterize its molecular weight one must not only demmine its average chain length but the uniformity of its chain length as well. Again, the last few years have seen a great increase in industrial interest in determining the &in length array or distribution. Ten years ago scarcely any chain length uniformity measurements were being made in industry. Today, in spite of the fact that there is still no easy, convenient or satisfaetorilyprecise way to make such determinations, w e find severalindustrial laboratories making hundreds of theaa estimations each year in order to gain insight into the qualities of their cellulosic products. It is the function of this symposium to bring about a meeting of thoughts and a discussion of ideas to further advance the industrial adoption and application of newer techniques for molecular weight and molecular weight uniformity measurementa. I t will indeed be a step forward if we are able to enwurage lhe adoption of a somewhat more uniform technique for making theaa measurementa so that the terms intrinsic viscosity, DP, and DP uniformity will m e a n approximately the name thing to various people in different cellulose research laboratories about the country or even within the same laboratory.
R. L. MITCHELL
RECCNT WORK ON MOLECULAR WEIGHT. 8. G. Ranby, and H. F. Mmtk..
E. H. Immergul, ......................... INTRINSIC VISCOSITY OF NITROCELLULOSE. Chor1.r H. l i n d h y and May B. Fmnk.. .......................... INTRlNSlC VISCOSITY. A. F. Martin.. ....................
2483
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2491 2497
INTRINSIC VISCOSITIES AND MOLECULAR WEIGHTS OF CELLULOSE AND CELLULOSE DERIVATIVES. E. H. lmmergutand F. Eirich.. 2500
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..... 251 1 .......................... A. Mudhrnnd " N' ..................2522 PRECIPITATION FRACTIONATION OF CELLULOSE NITRATE. MOLECULAR WEIGHT UNIFORMITY.
Cod M. Conmd..
NITRATION AND FRACTIONATION O F RAYONS. W. E. Rosewan and Louise POOW. 251 8 SUMMATIVE CuPRIETHnENEDIAMINE FRACTIONATION, w, Rog*n"""""
R. 1. Mikhell
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FRACTIONAL SEPARATION.
R o b r t 1. S c d l . .
2526
............. 2 5 3 2
