54 
BULLETIN 691, U. S. DEPARTMENT OE AGRICULTURE. 
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 is weighed, allowing it to cool 
in a thin layer around the lower part of the flask. If difficulty is still experi- 
enced 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 thoroughly, after which it is 
corked and set aside for 30 minutes. 
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 ap- 
plied when the filtration by gravity almost 
ceases, but should be used sparingly, as it 
tends to clog the filter by packing the pre- 
cipitate 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 in- 
soluble 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 in- 
soluble is reported upon the basis of total 
bitumen taken as 100. 
The difference between the material in- 
soluble in carbon disulphide and in the 
naphtha is the bitumen insoluble in the 
latter. Thus, if in a certain instance it is 
found that the material insoluble in carbon disulphide amounts to 1 per cent 
siid that 10.9 per cent is insoluble in naphtha, the percentage of bitumen insol- 
uble would be calculated as follows : 
Fig. 7. 
Bitumen insoluble in naphtha _ 10.9- 
Total bitumen ~ 100-1 
— qq = 10 per cent 
MELTING POINT. 
[A. S. T. M. Tentative Standard D36-16T.1 
1. The ring and ball method shall be used. (Fig. 7.) 
2. The apparatus shall consist of a brass ring 15.875 mm. (five-eighths inch) 
in diameter, 6.35 mm. (one-fourth inch) deep, 2.38125 (three thirty-seconds 
inch) wall, suspended 25.40 mm. (one inch) above bottom of beaker; a steel 
ball 9.525 mm. (three-eighths inch) in diameter, weighing between 3.45 and 
3.50 g. ; a standardized thermometer ; a glass beaker, approximately 600 cc. 
capacity. 
3. Carefully melt tlie sample and fill the ring with the material to be tested. 
Remove any excess. Place the ball in the center of the ring and suspend in the 
