144, 145] Quantitative Analysis of Oil Cakes 99 



off the stretched linen. The capsule is dried in the steam 

 oven until it ceases to lose weight. 



The fibre thus estimated will contain whatever sand there 

 is in the 3 grams of cake used. It is therefore transferred to 

 a weighed platinum dish, burned, and the weight of the ash 

 taken. This is subtracted from the total weight of the fibre. 



144. Albuminoids. — If the percentage of nitrogen be 

 multiplied by 6*25, the percentage of albuminoid matter is 

 obtained. 1 



It is, therefore, only necessary to estimate the nitrogen in 

 the cake. This is done by either the soda lime (paragraphs 

 86-89) or the sulphuric acid process (paragraphs 90-95), using 

 about 1 gram of the cake. 



145. Remarks on Cake Analysis.— Should the opera- 

 tions described in paragraphs 137-144 be performed one after 

 the other in the order given, it would take a very long time to 

 complete the whole analysis. The following method of proce- 

 dure will enable the student to complete the analysis in the 

 minimum time : 



1. Weigh out three portions of the ground-up sample as 

 follows : 



{a) About 2 grams in a porcelain capsule. 

 (b) About 3 grams on a watch glass. 

 {c) About 1 gram on a watch glass. 



2. Place (a) in the steam oven. 



3. Put (c) in a flask with strong sulphuric acid to estimate 

 the nitrogen. 



4. Prepare the Soxhlet's apparatus, and start the oil estima- 

 tion with (b). 



1 This factor 6*25 is based on the fact that the average percentage of 

 nitrogen in the albuminoids of vegetable foods is 16%. 



100-7-16 = 6-25. 



