54 



BULLETIlSr 691, U. S. DEPARTMENT OF AGEICULTURE. 



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 tben 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 gravitj'^ 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 

 and that 10.9 per cent is insoluble in naphtha, the percentage of bitumen insol- 

 uble would be calculated as follows : 



Bitimaen insoluble in naphtha _ 10.9 — 1 9.9_ 



Total bitumen ~ 100-1 ~ 99 ~ -^^ ^^^' ^^^* 



Fig. 7. 



MELTING POINT. 



[A. S. T. M. Tentative Standard D36-16T.] 



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 the 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 



