42 BULLETIN 314, U. S. DEPAETMENT OF AGBICULTL T EE. 



A 2-gram sample of this dehydrated material is extracted with car- 

 bon disulphide as described in the method for the determination of 

 bitumen soluble in carbon disulphide, and in this manner the organic 

 matter insoluble in carbon disulphide can be determined. A 1-gram 

 sample of the dehydrated material is ignited. The ash will contain 

 any inorganic matter from the bitumen as well as the fixed alkali 

 present in the soap. The results are ; of course, all calculated on a 

 basis of the original material. 



Many emulsions contain ammonia, and when this is present a second 

 distillation of the material is necessary. This is carried out on a 100- 

 gram sample in exactly the same manner as described for the deter- 

 minations of water, excepting for the fact that 40 cubic centimeters 

 of a 10 per cent solution of caustic potash is added to the contents of 

 the retort before beginning the distillation. The distillate is collected 



N 

 in a measured volume of ~- sulphuric acid. When the distillation is 



. N . 



completed the excess of acid is titrated with -~ caustic potash, and the 



ammonia thus determined. 



Having determined all constituents as above noted, it is assumed 

 that the difference between their sum and 100 per cent is bitumen, 

 which amount is reported accordingly. 



