28. BULLETIN 314, U. S. DEPARTMENT OF AGRICULTURE. 
than 15 minutes is necessary, and the following method proposed by 
the Committee on Standard Tests for Road Materials of the American 
Society for Testing Materials is recommended: ! 
From 2 to 15 grams (depending on the richness in bitumen of the substance) is 
weighed into a 150-cubic centimeter Erlenmeyer flask, the tare of which has been 
previously ascertained, and treated with 100 cubic centimeters cf carbon disulphide. 
The flask is then loosely corked and shaken from time to time tntil practically all 
large particles of the material have been broken up, when it is set aside and not dis- 
turbed for 48 hours. The solution is then decanted off into a similar flask that has 
been previously weighed, as much of the solvent being poured off as possible without 
disturbing the residue. The first flask is again treated with fresh carbon disulphide 
and shaken as before, when it is put away with the second flask and not disturbed for 
48 hours. 
At the end of this time the contents of the two flasks are carefully decanted off 
upon a weighed Gooch crucible fitted with an asbestos filter, the contents of the sec- 
ond flask being passed through the filter first. The asbestos filter shall be made of 
ignited long-fiber amphibole, packed in the bottom of a Gocch crucible to the depth 
of not over one-eighth of an inch. After passing the contents of both flasks through 
the filter, the two residues are shaken with more fresh carbon disulphide and set aside 
for 24 hours without disturbing, or until it is seen that a good subsidation has taken 
place, when the solvent is again decanted off upon the filter. This washing is con- 
tinued until the filtrate or washings are practically colorless. 
The crucible and both flasks are then dried at 125°C. and weighed. The filtrate 
containing the bitumen is evaporated, the bituminous residue burned, and the 
weight of the ash thus obtained added to that of the residue in the two flasks and the 
crucible. The sum of these weights deducted from the weight of substance taken 
gives the weight of bitumen extracted. 
s 
USE GF TOTAL BITUMEN DETERMINATION. 
This determination is made on all classes of bituminous products. 
In the analysis of tars the organic matter insoluble is commonly 
known and reported as ‘‘free carbon.” 
DETERMINATION OF BITUMEN INSOLUBLE IN PARAFFIN NAPHTHA. 
EQUIPMENT. 
The apparatus is the same as for bitumen soluble in carbon disulphide. 
METHOD. 
This determination is made in the same general manner as the 
total bitumen determination, except that 100 cubic centimeters of 
86° to 88° B. paraffin naphtha, at least .85 per cent distilling be- 
tween 35° C. and 65° C., is employed as a solvent instead of carbon 
disulphide. Considerable difficulty is sometimes experienced in 
breaking up some of the heavy semisolid bitumens; the surface of the 
material is attacked, but it is necessary to remove some of the 
insoluble matter in order to expose fresh material to the action of 
the solvent. It is, therefore, advisable to heat the sample after it 1s 
weighed, allowing it to cool in a thin layer around the lower part of 
1 Proc. Am. Soc. for Testing Materials, 1909, Vol. IX, p. 221. 
