

EXAMINATION OF BITUMINOUS EOAD MATEEIALS. 21 



DISTILLATION TEST. 



EQUIPMENT. 



1 250 cubic centimeter Engler distillation flask. 



1 chemical thermometer reading from 0° C. lo 400° C. 



1 short condenser, with rubber tubing. 



6 25 cubic centimeter glass cylinders, graduated to 0.2 cubic centimeter, 



1 iron ring support (ring 7.5 cm. in diameter). 



l'iron tripod. 



1 burette clamp. 



1 tin shield. 



1 pinchcock. 



2 Bunsen burners, with rubber tubing, 

 1 quart tin cup, seamless. 



1 pint tin cup, seamless. 



1 rough balance, capacity 1 kilogram, sensitive to 0.1 gram. 



1 analytical balance, capacity 100 grams, sensitive to 0.1 milligrams. 



METHOD. 



The Engler flasks for this test should meet the following require- 

 ments: 



Diameter of bulb 8. c. m. 



Length of neck 15. c. m. 



Diameter of neck 1. 7 c. m. 



Length of tubulature 15. c. m. 



Diameter of tubulature 0. 9 c. m. 



Angle of tubulature 75° 



A 3 per cent variation from the above requirements is allowed. 



Thermometers should be thoroughly annealed and filled with 

 carbon dioxide or nitrogen under pressure. The mercury column 

 should rise from 15° to 95° in not more than five seconds, when 

 plunged into boiling water. 



The thermometers are calibrated by setting up the entire apparatus 

 (fig. 12) as though a distillation of tar were to be made. One hun- 

 dred cubic centimeters of material of known boiling point is placed 

 in the flask, which is then heated until the contents distil over at a 

 uniform rate and the thermometer indicates a constant temperature, 

 which is noted. By using three different materials of widely vary- 

 ing boiling point, three calibrations on the thermometer scale are 

 obtained from which other intermediate points may bo plotted. 

 The coiicct fractionating points for the calibrated thermometer are 

 then ascerl ained. 



For calibrating thermometers in the laboratories of the Office of 

 Public Roads and liural Engineering the fractionating points are ob- 

 tained from the distillation of distilled water (boiling point 100° C), 

 chemically pure naphthalene (boiling point 218.2° C), and chemi- 

 cally pure benzophenone (boiling point 305° C). The boiling point, 

 of course, varies wiili the barometric pressure, but if the thermome- 

 ter! are calibrated al a time when the barometer indicates about the 



