No. 2,130,948

There are only a few major raw materials of which the U. S. does not have its own supplies. Such are rubber and tin.

Such also is silk. Last week, however, the U. S. awarded Patent No. 2,130,948 to the late W. H. Carothers, former chemist for E. I. du Pont de Nemours & Co.

The apparel trade, which had for some time heard rumors of the new Du Pont product under the name of Fibre 66, believed it might prove the first practical process for manufacturing synthetic silk entirely from chemicals.

When rayon appeared it was at first hoped that it would completely replace silk as raw material. It never did because, among other reasons, it lacked silk's elasticity (a rayon stocking, for example, wrinkles instead of clinging to the knee and sharp-eyed women maintained they could tell the difference at a glance). The new fibre (made of complex nitrogen compounds, among them cadaverine*), as silky as silk itself, can be produced in sizes one-tenth to one-seventy-fifth finer than silk filament, and in some sizes has 150% greater tensile strength. Its elasticity is such that it can be stretched up to 700% of its normal length. So far no one has attempted to produce it commercially. Hence chemists do not know what it will cost, though it is estimated it will be somewhat dearer than rayon, may cost even as much as silk. If it could be manufactured inexpensively, however, it seemed likely to threaten silk's last big U. S. market--the hosiery industry, which last year turned $73,230,000 worth of raw silk into women's stockings.

* Cadaverine is a poison formed by dissolving proteins and putrefying animal tissues.

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