58 



BULLETIN 691^ U. S. DEPARTMENT OF AGEICULTUEE. 



5. Method. — One hundred cubic centimeters of the dehydrated material to be 

 tested shall be placed in a tared flask and weighed. After adjusting the ther- 

 mometer, shield, condenser, etc., the distillation is commenced, the rate being 

 so regulated that 1 cc. 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 100° 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 when distillation is complete. Dur- 

 ing the distillation the condenser tube shall be 

 warmed when necessary to prevent the deposition 

 of any sublimate. The percentages of fractions 

 should be reported both by weight and by volume. 



SAMPLES AND SAMPLING. 



The following directions for selecting and ship- 

 ping samples of bituminous materials should be fol- 

 lowed in connection with materials which are to be 

 tested, in the laboratory, for conformity with the 

 foregoing specifications. 



GENERAL DIRECTIONS. 



(1) Samples should be 

 taken so as to represent 

 as nearly as possible an 

 average of the bulk of ma- 

 terial sampled and should 

 also be selected with a view 

 to ascertaining the maxi- 

 mum variation in char- 

 acteristics which the mate- 

 rial may possess. (2) Care 

 should be taken that the 

 samples are not contami- 



D=l 



Fig. 8. — Distillation apparatus. 



nated with dirt or any other extraneous matter and that the sample containers 

 are perfectly clean and dry before filling. (8) Immediately after filling, the 

 sample containers should be tightly closed and properly marked for identifica- 

 tion, the identification being placed on the container itself and not on the lid 

 unless both container and lid are marked. (4) Samples should be packed 

 for shipment >n such manner that leakage of contents or contamination by 

 excelsior, paper, or other packing material during transit is entirely prevented, 

 as well as obliteration or removal of the identification marks. (5) Notifica- 

 tion of shipment of samples, with statement of identification marks and such 

 other descriptive information as may be necessary, should be promptly for- 

 warded to the laboratory. 



FREQUENCY OF SAMPLING. 



(1) Each consignment of bituminous material should be sampled. (2) Ad- 

 ditional samples should be taken whenever the material changes materiallj' in 



