A Simplified Oxygen-Flask Combustion Procedure for Polymer Analysis The Schoniger combustion techniq~e',~ is a simple, rapid and reasonably precise method for the analysis of polymers containing chlorine3,sulfur4,phosphorus4, or radiotra~ers~.~, and as such is eminently suited to undergraduate experimentation. However, in our experience, a major drawback to this technique is that the platinum gauze ignition assembly is very costlv and is hiehlv suscentible to nhvsical damaee bv inexnerienced users. ~'cently we&umve~ted this problem by midf;ing the eap~rimentaltechnique to omit the platinum gauze holder. Cornhuntion 18rarried out in a dry 500-ml flask with theaqueous absorbingsolurion contained in a test rubeofappropriate dimensions (see figurel. The weighed polymer sample (:-10 mg), wrapped in an appropriately shaped, ash1e.w filter papr7,
Analysis of Commercial PVC
Test tubcvith Okorbmt
-500 ml RB or FB
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Chlwine Content (%w/w) Platinum @we Modified Theoretical Memod Method Value 58.7+ 1.1.
57.9
+ 1.1.
56.7
'Meen and s t a M deviation d Rve sapsrate dstermlnatlms.
Modified oxygen flask assembly.
hplc is ignited and dropped into the oxygen-flushed flask, which is immediately dased with a greased stopper. When the sample has fully comhusted, the flask is gently tilted so as to pour the absorbent inta the base of the flask. After a further 1&15 minutes the stopper is removed and the contents of the flask are prepared for titration. We have used this method successfully for undergraduates analyzing trace chlorine in polystyrene as part of a study in chain-transfer kinetics7. The efficacy of this approach versus the conventionalSchoniger stopper technique is demonstrated in the table for the analysis of the chlorine content of PVC. The analyses were performed on 5-mg samples by an assistant previously unfamiliar with the technique. The results show that the modified method is an excellent, low-cost alternative to the conventional approach for analysis of polymer samples.
' Schanlger, W.. Mikmchim. Acla.. 123 (1955).
Schaniger. W.. Mikmchim. Acte, 869 (1956). 'Haslan, J., Hamilton, J. B., and Squinell, D. C. M., J. Appl. Chem., 10, 97 (1960). Macdonald. A. M. G.. and Stephen. W. I.. J. CHEM. E m . . 39.528 (1962). Can, R. J., and Gordon, B. E., J. P o h m Scl., CB, 71 (1965). 'Yana.J. Y.. J. Polvmersci...64.31 . 119661 . McCaffery. E. L.. "Labwatwy Preparation fw Macmmolecular Chemistry," McGraw-Hill. New Ywk, 1970.
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David R. Burfield Swee-Cheng Ng University of Malaya Kuah Lumpur 22-11, Malaysia
Volume 61
Number 10
October 1964
917
