. Bulletin of the Department of Agriculture. Agriculture; Agriculture. SAMPLING AND TESTING HIGHWAY MATERIALS. 37. This pycnometer consists of a conical or Erlenmeyer-shaped flask about cm. high, cm. diameter at bottom, and cm. diameter at the mouth. It is care- fully ground to receive an accurately fitting solid glass stopper with a hole about 1 mm. bore in place of the usual capillary opening. The lower surface of this stopper is made concave to allow air bubbles to escape through the bore. The depth of the cup-shaped depression is mm. at the center. The flask has a capa
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. SAMPLING AND TESTING HIGHWAY MATERIALS. 37. This pycnometer consists of a conical or Erlenmeyer-shaped flask about cm. high, cm. diameter at bottom, and cm. diameter at the mouth. It is care- fully ground to receive an accurately fitting solid glass stopper with a hole about 1 mm. bore in place of the usual capillary opening. The lower surface of this stopper is made concave to allow air bubbles to escape through the bore. The depth of the cup-shaped depression is mm. at the center. The flask has a capacity of about 25 c. c. and weighs when empty about 25 grams. Its principal advantages are (1) that any de- sired amount of bitumen may be poured in without touching the sides above the de- sired level; (2) it is easily cleaned; (3) on account of the mm. bore the stopper can be easily inserted when the flask is filled with a viscous oil. When working with semisolid bitumens which are too soft to be broken and handled in fragments, the following method of determining their specific gravity is employed: The clean, dry pycnometer is first weighed empty, and this weight is called a. It is then filled in the usual manner with freshly distilled water at 25° C, and the weight is again taken and called b. A small amount of the bitumen should be placed in the spoon and brought to a fluid condition by the gentle application of heat, with care that no loss by evaporation occurs. When sufficiently fluid, enough is poured into the dry pycnometer, which may also be warmed, to fill it about half full without allowing the material to touch the sides of the tube above the desired level. The flask and contents are then allowed to cool to room temperature, after which the tube is carefully weighed with the stopper. This weight is called c. Distilled water, at 25° C, is then poured in until the pycnometer is full. After this the stopper is inserted, and the whole cooled to 25° C. by a 30-min
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