DETERMINING GREASE AND DIRT IN WOOL. 11 
final difference was 2.7 grams in the case of sample 1. Using the 
air-dry weights of the less-moist samples as the basis for percentages, 
this difference of 2.7 grams amounts to only 0.99 per cent of the air- 
dry weight of the original sample, and the average difference of 1.2 
grams is only 0.43 per cent of the average air-dry weight of the less- 
moist samples, while the smallest difference of 0.1 gram in the case 
of sample 8 amounts to only 0.037 per cent, all of which are negligible. 
In view of the fact that these experiments showed no advantage 
in conditioning wool at a higher temperature, it was decided to con- 
dition samples at 50° C. The object is to obtain a basic or " condi- 
tional" weight, and on the basis of these experiments, 50° C. for three 
hours seemed to offer this condition when there is no more than 20 
per cent of moisture in the air-dry samples. In the experiments here 
reported, 20 per cent moisture was the largest percentage for any of 
the samples used. Results of these experiments prove that the dry- 
ing of wool samples containing no more than the usual amount of mois- 
ture for three hours at 50° C. is sufficient to remove all excess of 
moisture that would cause an appreciable error in the determination 
of grease, dirt, and clean- wool contents of raw wool. 
DETERMINING WEIGHT OF GREASE. 
The preceding discussion shows that in order to bring the samples 
to a constant-moisture content it is necessary to condition them 
three times before each of the three weighings in the process. It is 
equally important that all the grease be removed between the first 
and second conditionings in order to obtain the grease content 
distinct from the dirt. 
The results of tests, involving a series of gasoline treatments on 
20 Rambouillet and 20 crossbred 3 fleece samples (in which was shown 
the percentage of grease removed by each gasoline extraction until 
free from grease), form the basis for other tests to determine the 
exact number of treatments necessary to remove all grease. Table 5 
shows the results from the 20 Rambouillet and the 20 crossbred 
wool samples. 
8 The crossbred sheep used in this investigation are the result of matin? Rambouillet ewes with rams 
of coarse-wool breads, and the interbreeding of such crosses; also sheep of the Corriedale breed. 
