742 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



It is expected in the following year to continue the laboratory 

 study of slags and cements in connection with service experiments 

 to determine the best means of utilizing them as road material. 



CHEMICAL TESTS. 



The work of the past fiscal year under this project comprised (1) 

 the routine examination and analyses of bituminous and other road 

 materials; (2) the standardization of the methods of examination of 

 bituminous road materials; (3) chemical investigations and re- 

 searches; (4) instruction of student and highway engineers in the 

 chemistry of road materials; (5) the preparation ot Government 

 publications and various technical papers; (6) lectures and ad- 

 dresses; (7) the preparation of specifications for bituminous and 

 other road materials; and (8) the inspection and supervision of 

 bituminous road work and advice furnished thereon. 



During the year 824 samples of various materials were received 

 for examination in the chemical laboratories. This is nearly twice 

 the number examined during the fiscal year 1910 and over four times 

 the number examined in 1^9. Of these, 38 were reduced and re- 

 sidual petroleums, distillates, etc., 88 oil asphalts, blown oils, and 

 cut-back oil asphalts, 4 malthas, 32 native asphalts and fluxed native 

 asphalts, 3 emulsifying oils and emulsions, 36 crude and refined 

 water-gas tars, 47 crude and refined gas-house coal tars, 28 coke-oven 

 tars, 2 crude and refined wood tars, 3 tar and asphalt mixtures, 6 

 rock asphalts and bituminous aggregates, 21 rocks, cements, brick, 

 and gravel, and 16 miscellaneous materials not included under the 

 above headings. A number of these analyses were made in conjunc- 

 tion with experimental field work of the office, and were reported in 

 connection with these field experiments in Circular No. 94. 



Considerable progress was made in the standardization of methods 

 of examining bituminous road materials and valuable work in this 

 connection was carried on in cooperation with a special committee 

 of the American Society for Testing Materials, which has been at 

 work along this line for a number of years past. A detailed descrip- 

 tion of routine methods in use in this laboratory was published in 

 Bulletin No. 38, and about 20 methods are thus standardized for the 

 office at present. It is believed that this work will aid materially in 

 ihe adoption of uniform methods by other laboratories in this country 

 which are interested in such examinations. This is a matter of the 

 utmost importance at present. 



While the increase in the number of samples tested during the 

 year shows a considerable growth in the amount of routine work 

 accomplished in the chemical laboratory, investigative work relative 

 to the production and testing of bituminous material has not been 

 neglected. Some results relating to the method for the determination 

 of soluble bitumen and the composition of residues obtained in this 

 determination, together with the results of a preliminary investiga- 

 tion on the effects of naphthalene in tars, have already been 

 published. 



The economic utilization of various coke-oven tars in the prepara- 

 tion of road binders has also been given consideration, and the re- 

 sults of this investigation will appear shortly in the form of a Gov- 

 ernment publication. Among other problems of a progressive nature 



