SAMPLING AND TESTING HIGHWAY MATERIALS. 
59 
down by the addition of a 10 per cent solution of calcium chloride. The separated 
bituminous material is then kneaded by hand to separate all contained water and then 
subjected to the usual quality tests. 
37. DETERMINATION OF PARAFFIN SCALE. 
It is recommended that the paraffin scale determination be omitted on account of 
difficulty encountered in obtaining dependable results due to the inaccuracy of any 
methods which have heretofore been introduced. 
38. STANDARD METHOD FOR DISTILLATION OF CREOSOTE. 
(Extract from A. S. T. M. Standard Method, Serial Designation: D 38-1S.) 
(1) (a) Retort. — This shall be a tubulated glass retort of the form and approximate 
dimensions shown in figure 32, with a capacity of 250 to 290 c. c. The capacity shall 
Fig. 
-Asbestos shield. 
be measured by placing the retort with the bottom of the bulb and the end of the 
offtake in the same horizontal plane, and pouring water into the bulb through the 
tubulature until it overflows the offtake. The amount remaining in the bulb shall be 
considered its capacity. 
(b) Condenser tube.— The condenser tube shall be a suitable form of tapered glass 
tubing of the following dimensions: Mm 
Diameter of small end (permissible variation, 1.5 mm.) 
Diameter of large end (permissible variation, 3 mm.) 
Length (permissible variation, 4 mm.) 
12.5 
28. 5 
3(50. 
