In an effort to develop a simple and rapid means of measuring swelling capacities in water of cotton and other fibers in mass, the centrifuge technique has been subjected to a rather extensive study. In this technique the swelling capacity appears as a function of the moisture retention after swelling and centrifuging.Many previous workers have employed the centrifuge empirically for the removal of external, nonswelling water from fibers, but under conditions which have varied greatly as to time and intensity of centrifuging. In the present work, the complication of dealing with the two variables of time and speed of centrifuging simultaneously has been circumvented by noting that straight lines (to a high degree of approximation) were obtained when the moisture regains of the sample were plotted against the squares of the rotational speeds. The intercept of these straight lines on the moisture regain axis was characteristic for a given fiber in a given physical form. The intercept values were shown to be the same and reproducible for any selected centrifuging time of 20 min. or more, provided the minimum acceleration was above 3,200 g.It was found that the zero-speed intercepts on the moisture regain axis, while highly reproducible, did not represent true swelling capacities. That the intercept values were too large was shown by the sizable intercepts obtained with glass fibers, which obviously are incapable of swelling.It was found that the excess moisture retentions could be reduced considerably in samples "oriented" so that the axis of the yarns or cords lay parallel to the direction of centrifugal force. Still further reductions occurred on cutting such "oriented" samples after centrifuging and determining the moisture regains of the cut lengths nearest the centrifuge axis.

Yarns manufactured from samples of the same six cotton varieties discussed in the previous paper were partially acetylated to an acetyl content of approximately 24% while held under tension. Certain physical properties of the component fibers, fiber bundles, and yarns were then measured. The changes in most properties were found to be associated with differences in the cottons and the acetyl contents. The averages for breaking loads and tenacities of the fibers were decreased while their linear densities and secant moduli were increased. Breaking loads, linear densities, and secant moduli of the yarns were increased. Elongation of the yarns at break was decreased, while tenacity remained essentially unchanged. The changes were greater for some cottons than for others; whether the changes were advantageous or disadvantageous would depend somewhat upon the use to which acetylated cotton is to be put.

Yarns from six cottons selected for their widely different inherent fiber characteristics were mercerized (1) under sufficient tension to maintain their original length, and (2) while permitted to contract freely. Fibers were removed from the yarns and were sub jected to certain physical measurements. Moisture regain, cellulose density, linear den sity, breaking load, and elongation at break were measured on either or both fibers and yarns. Samples of the different cottons were found to differ in their response to the treatment. Those samples with a low value in a property generally displayed the greatest per cent change in that property. Large differences in the properties of the fibers and yarns were associated with the condition of mercerization whether at constant length or slack. Mercerization tended to equalize differences between the properties of fibers in a sample as well as between those of different samples.

Six varieties of cottons were given certain chemical treatments, and the resulting changes in their fundamental physical properties were measured. This first report of a series describes the purpose of the work, the methods used to measure the properties, and the types of chemical treatments used. It also furnishes photomicrographs of cross sections of the cotton fibers and the values of the physical properties of the untreated cottons, which are the controls for samples receiving the chemical treatments. Data are given for yarns and fibers of these cottons, and comparisons are made between values of corresponding properties.