Analysis of Weighted Silk

Abstract

A GENERALLY applicable, rapid, and convenient method for the determination of the amount of pure silk fibre in silk textiles is described. Weighting and finishing materials are removed by repeated extractions with hot water, 2 per cent sodium carbonate solution and a solution containing 2 per cent of hydrochloric and 2 per cent of hydrofluoric acids. Results of analyses of samples of known composition are presented which indicate that the results are correct to within 1 per cent of the weight of the dried finished material. Results obtained by inexperienced analysts working in different laboratories have been in good agreement when samples of the same silk were analyzed. Qualitative methods for the identification of the following weighting materials are given: Aluminum, lead, phosphate, silica, tin, zinc.

Get full access to this article

View all access options for this article.

References

Fifty-seventh Annual Report, Silk Association of America , New York, p. 27, 1929.

The Joint Committee of the Textile Industry on Weighted Silk, composed of representatives from national associations representing manufacturers, distributors, and users, established this smaller technical committee to consider technical problems.

Anon , To find silk weighting content, 1'e.vtile World, vol. 76, p. 1454, Sept. Sept. 14, 1929.

Unpublished data of the Technical Committee on Weighted Silk.

Gnehm, R. , and Blummer, E. , Methode pour le dosage de la charges des soies noires, Rev. gen. mat. color., vol. 2, pp. 133-134, April, 1898.

Branegan, James A. , Practical analysis of methods for determination of artificial weighting of tin-weighted silk. Melliand, vol. 1, pp. 735-739, August, 1929. Compares results obtained with several methods of analysis.

Gnehm, R. , Eine neue Methode zur quantitativen Bestimmung der Zinn-Phosphat-Silicat-Charge auf Seide, Z. Farben-Textil-Chem., vol. 2, pp. 209-210, June 1, 1903.

Suggested informally several years ago by Dr. Victor Froelicher, chief chemist, Textile Dyeing Co. of America.

The author is indebted to Dr. Victor Froelicher for the samples of known weighting content representative of the different types of weighting

10.

These results were obtained under the supervision of Prof. Pauline Beery Mack, of the department of home economics, Pennsylvania State College.

11.

This reagent may conveniently be prepared by mixing equal volumes of 4 per cent (± 0.1 per cent) hydrofluoric and 4 per cent (± 0.1 per cent) hydrochloric acids. High concentrations of mineral acids disintegrate silk. Too low a concentration may not remove inorganic materials sufficienly well from all types of weighted silk fabrics. For this work the concentration of each of the acids was determined by titration with a stand ard base. The concentrations given mean per cent by weight of actual HF and HCl (not of the ordinary concentrated acids). The reagent is approximately N with respect to HF and N/2 with respect to HCl.

12.

Prescott, Albert B. , and Johnson, Otis C. , Qualitative Chemical Analysis, 7th ed., thoroughly revised, 436 pp., 1916. D. Van Nostrand Co., New York. Scott, Wilfred W. , Standard Methods of Chemical Analysis, 4th ed., vol. 1, 745 pp., 1925. D. Van Nostrand Co., New York. Hillebrand, W.F. , and Lundell, G.E.F. , Applied Inorganic Analysis, 929 pp., 1929. John Wiley & Sons (Inc.), New York.