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 38-18.) 



(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 



T 



Fig. 33.— 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.) 12. 5 



Diameter of large end (permissible variation, 3 mm.) 28. 5 



Length (permissible variation, 4 mm.) 360. 



