64 REPORTS ON THE STATE OF SCIENCE.—1918. 
An interesting investigation has recently been carried out by 
Clayton, Beadle & Stevens on the swelling of artificial silk in caustic 
soda solutions. > It was found that the swelling increased with the 
concentration of alkali up to a certain point and then decreased. 
This change is very similar to that observed by Procter with gelatine 
and hydrochloric acid. Procter’s method of investigation cannot be 
applied in this case since the concentration of alkali used is too high. 
It was shown that the addition of sodium chloride to the caustic soda 
diminished the swelling and adsorption of alkali. The author found 
that if the artificial silk was first treated with the caustic soda and 
then with a salt solution the amount of swelling was considerably 
decreased, but practically no caustic soda passed into the salt solution, 
It is, of course, known that sodium chloride ‘salts out’ caustie soda 
from solution. 
(J) Artificial Silk. 
1 Suvern, Die Kunstliche Seide, Berlin (1900). 
? Herzog, Untersuchung der naturlichen und Kunstlichen, Seiden (1910). 
3 Gaidukow, Koll. Zeit., 6, 260 (1910). 
4 Clayton, Beadle & Stevens, 8¢ Int. cong. Chem. 13, p. 25. 
® Clayton, Beadle & Stevens, Journ. Soc. Dyers and Cols., 30, 244 (1914). 
® Ost, Zeit. f. angew. Chem., 31, p. 141 (1918). 
7 Wilson, Journ. Soc. Chem. Ind., 817 (i917). 
Wool. 
The products formed by the hydrolysis of wool have been 
determined,! but nothing is known of the constitution of the 
substances of the wool fibre itself. The presence of a free amido 
group in the substance of the wool fibre has been discussed from time 
to time without any very definite conclusions being arrived at.? 4 8 
It has recently been shown that wool fibres are not chemically 
homogeneous, the outer layers being more resistant to the action of 
chemical reagents than the inner parts.° ® 
By treatment of wool with solutions of caustic alkalies a colloidal 
solution is obtained,’ which forms precipitates with dyestuffs.°-4 
These precipitates have been considered to be definite chemical 
compounds. ‘The process of precipitation reminds one more of the 
coagulation of colloidal solutions than of chemical combination. 
The colloidal state of wool fibres is considerably changed by 
boiling in water, the fibres becomiug more plastic; changes.in the 
internal strains are also produced.? 
When subjected to beating in presence of solutions of soap or of 
acids, wool fibres become matted together, the process being known 
as felting, fulling or milling. For many years felting has been 
considered to be due to the interlocking of the serrations present in 
wool fibres. This theory was supported by the fact that in some 
cases fibres with less serrations felted less easily than others with 
more, and that treatment with chlorine!! removed the serrations and 
prevented felting. There are, however, wool fibres having practically 
no serrations which can be felted, although with difficulty, but which’ 
are also prevented from felting by treatment with chlorine. Another 
theory has been brought forward! that the wool fibres become plastic 
and adhere together when subjected to beating. The fact that a 
fabric made of tightly-spun, straight wool fibres is very much more 
difficult to felt than one made of more loosely-spun material appears 
ices 
