52 BULLETIN 949, U. S. DEPARTMENT OF AGRICULTURE. 



The sensitiveness of the thermometer shall be such that when cooled to a tempera- 

 ture of 74° C. below the boiling point of water at the barometric pressure, at the time 

 of test, and plunged into free flow of steam, the meniscus shall pass the point 10° C. 

 below the boiling point of water in not more than 6 seconds. 



The thermometer shall be set up as for the distillation test, using water, naphthalene 

 and benzophenone as distilling liquids. The correctness of the thermometer shall 

 be checked at 0° and 100° C. after each third distillation until seasoned. 



(c) Condenser. — The condenser tube shall have the following dimensions: 



Mm. 



Adapter 70 



Length of straight tube 185 



Width of tube 12 to 15 



Width of adapter end of tube 20 to 25 



(d) Stands. — Two iron stands shall be provided, one with a universal clamp for 

 holding the condenser, and one with a light grip arm with a cork-lined clamp for hold- 

 ing the flask. 



(e) Burner and shield. — A Bunsen burner shall be provided, with a tin shield 20 cm. 

 long by 9 cm. in diameter. The shield shall have a small hole for observing the flame. 



(/) Cylinders. — The cylinders used in collecting the distillate shall have a capacity 

 of 25 c. c, and shall be graduated in 0.1 c. c. 



(4) The apparatus shall be set up as shown in figure 28, the thermometer being 

 placed so that the top of the bulb is opposite the middle of the tubulature. All con- 

 nections should be tight. 



(5) One hundred cubic centimeters of the dehydrated material to be tested shall 

 be placed in a tared flask and weighed. After adjusting the thermometer, shield, 

 condenser, etc., the distillation is commenced, the rate being so regulated that 1 c. c. 

 passes over every minute. The receiver is changed as the mercury column just 

 passes the fractionating point. 



The following fractions should be reported : 

 Start of distillation to 110° C. 

 110 to 170° C. 

 170 to 235° C. 

 235 to 270° C. 

 270 to 300° C. 

 Residue. 

 To determine the amount of residue, the flask is weighed again Avhen distillation 

 is complete. During the distillation the condenser tube shall be warmed when nec- 

 essary to prevent the deposition of any sublimate. The percentages of fractions 

 should be reported both by weight and by volume. 



32. STANDARD METHOD FOR DETERMINATION OF SOFTENING POINT 

 OF BITUMINOUS MATERIALS OTHER THAN TAR PRODUCTS (RING- 

 AND-BALL METHOD). 



(A. S. T. M. Standard Method, Serial Designation, D 36-19.) 



Note. — It was recommended by the conference that this method be followed 

 for both asphaltic and tar products. 



(1) The softening of bituminous materials generally takes place at no definite mo- 

 ment or temperature. As the temperature rises, they gradually and imperceptibly 

 change from a brittle or exceedingly thick and slow flowing material to a softer and 

 less viscous liquid. For this reason, the determination of the softening point must 



