5^6 Reading-Course for Farmers^ Wives. 



and are subsequently moistened and ironed dry with a hot iron. 

 Destructive results are then produced. 



The presence of starch lessens the destructive action of any of the 

 acids. 



Action of alkalis on cotton and linen. The action of alkalis on 

 cellulose differs from that of acids. Dilute washing soda solution, 

 borax and soap have little or no harmful action on cotton or linen, but 

 caustic soda or lye, as it is familiarly known, is more destructive to these 

 fabrics, especially at high temperatures and if allowed to act for any 

 length of time in the presence of air. If a fabric made from cotton 

 fibres is immersed for two minutes in a strong solution of caustic soda 

 it assumes a gelatinous appearance, and if it is then immediately removed 

 and washed free of the alkali it is found to have greatly shrunken and 

 to have become much closer and firmer in texture. This limited time 

 of action of the strong alkali actually strengthens the cloth. At one 

 time it was thought that this process would be very valuable in the 

 manufacture of textile goods, but it so increased the strength of the 

 fabric thus treated that the demand decreased and hence the operation 

 was discontinued as impractical for the manufacturer. A modification 

 of this process, know as mercerization, gives to cotton goods a glossy, 

 silky appearance without materially increasing its durability. It must 

 not be thought that because this limited action of strong alkali strengthens 

 the fabric that long-continued action will be harmless. The first effect 

 is strengthening, but if the action is continued beyond the brief time 

 mentioned it will gradually destroy the cloth. 



II. Wool. The hairy covering of a number of animals is called wool. 

 It is the most important animal fibre used in the manufacture of clothing. 

 When woolen cloth is washed it undergoes a characteristic shrinkage. 

 This shrinkage is increased by the use of strong soaps, by rubbing, by 

 quick changes in temperature while wet, by the use of strong alkalis, 

 by ironing with hot irons, etc. 



Wool fibre has a characteristic appearance and can readily be dis- 

 tinguished under the microscope from any of the other textile fabrics. 

 The surface of the fibre is seen to be covered with little horny scales all 

 running in one direction. 



In some wool fibres the surface is comparatively smooth and in others 

 the serrated edge is very conspicuous, according to the source of the 

 wool from which the fibre is obtained. Wool fibre has been shown to 

 be composed of numerous small segments called cells, whose overlapping 

 edges give the characteristic external horny layer. When woolen cloth 

 is wet, the fibre expands somewhat and there is a loosening of the pro- 



