42 BULLETIN 314, U. S. DEPARTMENT OF AGRICULTURE. 
A 2-gram sample of this dehydrated material is extracted with car- 
bon disulphide as described in the method for the determiation of 
bitumen soluble in carbon disulphide, and in this manner the organic 
matter insoluble in carbon disulphide can be determined. A l-gram 
sample of the dehydrated material is ignited. The ash will contain 
any imorganic matter from the bitumen as well as the fixed alkali 
present m 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 1s 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 begining the distillation. The distillate is collected 
} 
in a measured volume oi 5 
sulphuric acid. When the distillation is 
completed the excess of acid is titrated with 5 caustic potash, and the 
ammonia thus determined. 7 
Having determined ail constituents as above noted, it is assumed 
that the difference between their sum and 100 per cent is bitumen, 
which amount is reported accordingly. 
