58 
BULLETIN 691, U. S. DEPARTMENT OF AGRICULTURE. 
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- 
nated with dirt or any other extraneous matter and that the sample containers 
are perfectly clean and dry before filling. (3) 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 in 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 materially in 
Fig. 8. — Distillation apparatus. 
♦ 
