156 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



INVESTIGATION OF DUST PREVENTIVES AND ROAD BINDERS. 



During the past year the work of the Office relative to the inves- 

 tigation of the problems of dust prevention and road preservation 

 has advanced rapidly. 



Routine tests or analyses of bituminous road materials made in 

 the laboratories during the past year were more than double the 

 number made during the preceding year. A number of these 

 examinations were made in conjunction with the experimental field 

 work of the Office, and were reported, together with descriptions of 

 the experiments, in Circular No. 92. It is expected that these exam- 

 inations will be of great service in determining the value of certain 

 classes of binders, as the experimental work is carefully inspected 

 from time to time, and the results are made a matter of record. 



Through its laboratory work, the Office has been able to offer val- 

 uable advice in regard to specifications for bituminous road binders, 

 and in many instances to frame such specifications upon request of 

 various public-service bodies. A number of the state highway com- 

 missions have profited by this opportunity. 



Many worthless road preparations have been, and are at present 

 being, manufactured and sold to the public through ignorance on the 

 part of both producer and consumer with regard to the requisite 

 characteristics of such materials to meet local conditions. These 

 materials are sold under trade names and as a rule carry no valid 

 guaranty of quality. Specifications for such materials are therefore 

 much needed for the protection of the public, and this phase of the 

 work will be given continued attention by the Office. 



Special investigations of bituminous road materials carried on by 

 the laboratory have covered improvements in the methods of analysis, 

 the effect of various methods of distillation upon the physical and 

 chemical properties of tars, and the development of a test for deter- 

 mining the binding value of bitumens. 



CORROSION OF IRON AND STEEL. 



The investigations carried on by the Office relative to the corrosion 

 of iron and steel have induced some of the manufacturers to produce 

 a practically pure iron for culverts and pipes. While it is not possible 

 to produce an iron that will be entirely free from rust, yet it is 

 believed that these pure grades of metal are going to give very much 

 better service. 



Investigations in regard to fence wire have shown that wire fenc- 

 ing is not only made of inferior material, but that in many cases the 

 galvanizing is put on very thin. Some of the manufacturers have 

 already improved their products in these respects as a result of this 

 work. 



