6 BULLETIN 1100, U. S. DEPARTMENT OE AGRICULTURE. 
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 
