QQ DEPARTMENT BULLETIN 12 16, U. S. DEPT. OF AGRICULTURE 
46. METHOD OF TEST FOR PERCENTAGE OF BITUMEN 
INSOLUBLE IN PARAFFIN NAPHTHA 
1. This determination is made in the same general manner as the total 
bitumen determination, except that 100 cubic centimeters of 86° to 88° Baume 
paraffin naphtha, at least 85 per cent distilling between 35° and 65° C. is em- 
ployed as a solvent instead of carbon disulphide. Considerable difficulty is 
sometimes experienced in breaking up some of the heavy semisplid 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 is weighed, 
allowing it to cool in a thin layer around the lower part of the flask. If 
difficulty is still experienced in dissolving the material, a rounded glass rod will 
be found convenient for breaking up the undissolved particles. Not more than 
one-half of the total amount of naphtha required should be used until the 
sample is entirely broken up. The balance of the 100 cubic centimeters is then 
added, and the flask is twirled a moment in order to mix the contents thor- 
oughly, after which it is corked and set aside for 30 minutes. 
2. In making the filtration the utmost care should be exercised to avoid 
stirring up any of the precipitate, in order that the filter may not be clogged 
and that the first decantation may be as complete as possible. The sides of the 
flask should then be quickly washed down with naphtha and, when the crucible 
has drained, the bulk of insoluble matter is brought upon the felt. Suction may 
be applied when the filtration by gravity almost ceases, but should be used 
sparingly, as it tends to clog the filter by packing the precipitate too tightly. 
The material on the felt should never be allowed to run entirely dry until the 
washing is completed, as shown by the colorless filtrate. When considerable 
insoluble matter adheres to the flask no attempt should be made to remove it 
completely. In such cases the adhering material is merely washed until free 
from soluble matter and the flask is dried with the crucible at 100° C. for about 
one hour, after which it is cooled and weighed. The percentage of bitumen 
insoluble is reported upon the basis of total bitumen taken as 100. 
3. The difference between the material insoluble in carbon disulphide and in 
the naphtha is the bitumen insoluble in the latter. Thus, if in a certain instance 
it is found that rhe material insoluble in carbon disulphide amounts to 1 per 
cent and that 10.9 per cent is insoluble in naphtha, the percentage of bitumen 
insoluble would be calculated as follows : 
Bitu men insoluble in n aphtha _ 10.9— 1 _9.9_ 10 . 
Total bitumen ~ 100- 1 ~ 99 P 
47. METHOD OF TEST FOR LOSS ON HEATING OF OIL AND 
ASPHALTIC COMPOUNDS 
(A. S. T. M. standard method (£), serial designation D 6-27, except as indicated. 
See p. 1) 
1. This test covers the determination of the loss in weight (exclusive of 
water) of oil and asphaltic compounds when heated as hereinafter prescribed. 
The material under examination shall therefore first be tested for water, and 
if water is found to be present it shall be removed by suitable methods of 
dehydration before the material is subjected to the loss on heating test, or 
another sample shall be obtained which is free from water. 
APPARATUS 
2. The oven may be either circular or rectangular in form and may be 
heated by either gas or electricity. Its interior dimensions shall be as follows: 
Height, not less than 40.64 centimeters (16 inches) ; width and depth or diam- 
eter at least 5.08 centimeters (2 inches) greater than the diameter of the 
revolving shelf. 
It shall be well ventilated and shall be fitted with a window in the upper 
half of the door, so placed and of sufficient size to permit the accurate reading 
