DETERMIN^II^G GEEASE 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° G. 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^ 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. 



* The crossbred sheep used in this investigation are the result of mating Rambouillet ewes with rams 

 of coarse-wool breeds, and the interbreeding of such crosses; also sheep of the Corriedale breed. 



