Apr. IS, 1920 



Influence of Humidity upon Wool Fiber 



61 



coarser samples there is not such a tendency. This fact and the fact that 

 larger fibers can be more accurately measured with a micrometer caliper 

 make it possible to get satisfactory results for tensile strengths with sam- 

 ples of coarser wools. Then again the coarser wools have breaking 

 strengths which vary more closely with the areas of the cross section of 

 the wool than do the breaking strengths of fine wool samples, as is shown 

 in F-F of figure 3. The coarse wools may be measured from the original 

 lock, and their breaking and tensile strengths may be determined quite 

 satisfactorily. 



Sometimes it is necessary to make the closest possible comparison of 

 the effects of various conditions or chemical reagents on a given grade of 

 wool, as in the case at hand. The writer desired to determine the effects 

 of various humidities upon a uniformly mixed sample of wool. Single 

 fibers were drawn from sample B and placed consecutively in six different 

 groups, numbered i to 6, with their ends extending from one piece of 

 adhesive tape to another which was laid parallel to it and about 2^ 

 inches from it. Always beginning with No. i, these fibers were placed 

 one at a time in each of these six groups until 100 fibers, or the desired 

 number, were in each of the six small locks. By making five series of 

 these groups and subjecting the same numbers of each group to the 

 same test, it is possible to get some very satisfactory comparisons. 

 Although it is very tedious work, these fibers may be picked out by 

 hand at the rate of 200 an hour. Five small locks, each containing 120 

 fibers, were tested in the scoured condition at humidities of 40, 50, 60, 

 70, and 80 per cent and saturated. Similar locks were scoured with 

 ether and hot water and tested under the same conditions. The satu- 

 rated fibers were kept between moist filter papers until tested. 



Table IV and figure 4 show the results of this experiment. 



Table IV. — Elasticity and breaking strength of scoured and unsecured wool from 



sample B 



[Average of 600 fibers] 



Percentage of humidity. 



Scoured wool. 



Elasticity. 



Breaking 

 strength. 



Unsecured wool. 



Elasticity. 



Breaking 

 strength. 



40 



50 



60 



70 



80 



Saturated 



Per cent. 

 25. 80 

 30.76 



33-96 

 37.08 

 40. 08 

 33-76 



Dgm. 

 65. 14 

 64. II 

 64. 64 



59-53 

 60. 10 

 59.16 



Per cent. 

 26. 40 

 31.48 



34-72 

 38.00 



43-64 

 34.60 



Dgm. 

 69. 06 

 68.97 

 67. 01 

 63.80 

 60. 44 

 63.42 



The curve for unscourcd wool shows that the breaking strength de- 

 creases as the relative humidity changes from 40 to 80 per cent and in- 

 creases when the wool becomes saturated. In scoured wool the curve is 

 more irregular. There is a definite drop as the humidity changes from 



