143] Quantitative Analysis of Oil Cakes 97 



top of the steam oven, overheating being prevented by placing 

 two or three filter papers between the beaker and the metallic 

 surface of the oven. 



When the ether has all gone, the beaker is heated inside 

 the steam oven until it ceases to lose weight. The difference 

 between this final weight and the weight of the beaker gives 

 the weight of the oil. 



143. Estimation of Woody Fibre.— The portion of cake 

 which has been extracted with ether and dried in the cartridge 

 case is used for this estimation. It is transferred to a 16-oz. 

 beaker. If a portion adhere to the filter paper it may be 

 removed by opening the case and rubbing the adhering sub- 

 stance off with another part of the paper. When it is all in 

 the beaker 50 c.c. of a 5 per cent, solution of sulphuric acid 

 are added, together with 75 c.c. of distilled water. The beaker 

 is placed over a Bunsen burner, and the liquid raised to a boil. 

 As it approaches the boiling-point it must be watched care- 

 fully, as it has a tendency to froth up and boil over. As soon 

 as the frothing starts it should be stirred rapidly with a glass 

 rod, and, if the frothing become too violent, removed for a 

 moment from the burner. When all frothing has ceased any 

 particles of cake which adhere to the side are washed down 

 into the liquid with a small quantity of hot water, and the 

 solution is allowed to boil gently for half-an-hour. As the 

 liquid becomes more concentrated on boiling, it is necessary 

 to add a little hot water from time to time. The level of the 

 surface of the liquid may be marked by sticking a piece of 

 gummed paper on the outside of the beaker. It will then be 

 easy to see when more water ought to be added. At the end 

 of the half-hour the beaker is filled up with cold water and 

 allowed to stand for an hour. 



A clean piece of linen is placed over the top of a beaker, or, 

 better, a strong jam pot of about 20 oz. capacity. The liquid 



H 



