52 



BULLETIN 691, U. S. DEPARTMENT OF AGRICULTUEE. 



d-~- 



d 



inoters wide at the top. tapering to 3.6 centimeters at the bottom, and is 2.5 

 centimeters deep. 



For pi-oparing tlie felt the necessary appartatus is arranged as shown in 

 figure 6, in winch a is the filtering flask, & a rubber stopper, c the 

 filter tube, and d a section of rubber tubing which tightly clasps the Gooch 

 crucible c. The asbestos is cut with scissoi's into pieces not exceeding 1 

 centimeter in length, after which it is shaken up with just sufficient water to 

 pour easily. The crucible is filled with the suspended asbestos, which is 

 allowed to settle for a few moments. A light suction is then applied to di-aw 

 olf all the water and leave a firm mat of asbestos in the crucible. More of the 

 suspended material is added, and the operation is repeated until the felt is so 

 dense that it scarcely transmits liglit when held so that the bottom of the 

 crucible is between the eye and the source of light. The felt should then be 

 washed several times with water and drawn firmly against the bottom of the 

 crucible by an increased suction. The crucible is removed to a drying oven 



for a few minutes, after which it is ignited at 

 red heat over a Bunsen burner, cooled in a 

 desiccator, and weighed. 



From 1 to 2 grams of the bituminous material 

 is now placed in the Erlenmeyer flask, which has 

 been previously weighed, and the accurate 

 weight of tlie sample is obtained. One hundred 

 cubic centimeters of cliemically pure carbon 

 disulphide is poured into the flask in small 

 portions, with continual agitation, until all 

 lumps disappear and nothing adheres to the 

 bottom. The flask is then corked and set aside 

 for 15 minutes. 



After being weighed, the Gooch crucible con- 

 taining the felt is set up over the dry pressure 

 flask, as shown in the figure, and the solution 

 of bitumen in carbon disulphide is decanted 

 through the felt without suction by gradually 

 tilting the flask, with care not to stir up any 

 precipitate that may have settled out. At the 

 first sign of any sediment coming out, the decantation is stopped and the 

 filter allowed to drain, A small amount of carbon disulphide Is then washed 

 down the sides of the flask, after which the precipitate is brought upon the 

 felt and the flask scrubbed, if necessary, with a feather or " policeman," to 

 remove all adhering material. The contents of the crucible are washed with 

 carbon disulphide, until the washings run colorless. Suction is then applied 

 until there is practically no odor of carbon disulphide in the crucible, after 

 which the outside of the crucible is cleaned with a cloth moistened with a 

 small amount of the solvent. The crucible and contents are dried in a hot-air 

 oven at 100° C. for about 20 minutes, cooled in a desiccator, and weighed. If 

 any appreciable amount of insoluble matter adheres to the flask, it should also 

 be dried and weighed, and any increase over the original weight of the flask 

 should be added to the weight of insoluble matter in the crucible. The total 

 weight of insoluble material may include both organic and mineral matter. 

 The former, if present, is burned ofC by ignition at a red heat until no incan- 

 descent particles remain, thus leaving the mineral matter or ash. .which can 

 be weighed on cooling. The difference between the total weight of material 

 insoluble in carbon disulphide and the weight of substance taken equals the 

 total bitumen, and the percentage weights are calculated and reported as total 



Fig. 6. — Apparatus for determin- 

 ing soluble bitumen. 



