6 BULLETIX 1100, U. S. DEl^ARTMEXT OJ AGPJCULTUEE. 



final weight of clean wool found in the sample. For example, the 

 grease index is calculated by the following formula: 

 100 X weight of grease 

 weight of clean wool 



CONDITIONING FOR WEIGHING. 



The foregoing outline shows the need of three weighings of each 

 sample. It often happens that different classes of wools may be 

 handled at the same time and similar wools may be worked with 

 on days varying widely as to temperature and moisture. In order 

 to get useful data from the determinations made throughout the 

 year and with different wools, it is necessary to condition the wools 

 for each weighing in such way as to overcome the effect upon the 

 results of differences in natural moisture or of moisture contents as 

 affected by varying air conditions. Two samples of wool might 

 contain quite different quantities of moisture, due to their contents 

 of grease and foreign matter. The index figures would be based 

 upon final weight of clean wool. This index might be rendered in- 

 correct to the extent of 0.03 per cent in case conditioning was not 

 sufficient to bring these samples to a uniform moisture content, for 

 example : 



Sample A under natural conditions in air contains — 



Grams. 



Moisture 15 



Grease 20 



Dirt 40 



Clean wool 25 



Total weight 100 



Sample B has similar amounts of grease and clean wool, but 45 

 per cent of its weight in dirt and only 10 per cent moisture. The 

 true composition is then as follows: 



Grams. 



Moisture 10 



Grease 20 



Dirt 45 



Clean wool 25 



Total weight 100 



Results- of tests shown in Table 2-c indicate that imperfect condi- 

 tioning might remove 60 per cent of the moisture from sample A 

 and only 50 per cent from sample B. Calculation of the grease index 

 on this basis would therefore result as follows: 



Sample A, 60 per cent of 15 grams moisture removed equals 9 

 grams, leaving a remainder of 6 grams. 



Grams. 



Moisture 6 



Grease 20 



Dirt 40 



Clean wool 25 



Total weight of conditioned sample 91 



