8 



BULLETIN" 314, U. S. DEPARTMENT OF AGRICULTURE. 



closed by the cover b. To the conical bottom of a is fitted a conical 

 outflow tube c, exactly 20 millimeters long, with a diameter at the 

 top of 2.9 millimeters and at the bottom of 2.8 millimeters. This 

 tube can be closed and opened by the pointed hardwood stopper d. 

 Pointed metal projections are placed on the inside of a at equal dis- 

 tances from the bottom and serve for measuring the charge of mate- 

 rial, which is 240 cubic centimeters. The thermometer e is used to 

 ascertain the temperature of the material to be tested. The vessel 

 a is surrounded by a brass jacket/, which holds the material used as 

 a heating bath, either water or cottonseed oil, according to the tem- 

 perature at which 

 the test is to be 

 made. A tripod g 

 serves as a support 

 for the apparatus 

 and also carries a 

 ring burner lb by 

 means of which the 

 bath is directly 

 heated. The meas- 

 uring cylinder of 100 

 cubic centimeters 

 capacity, which is 

 sufficiently accurate 

 for work with road 

 materials, is placed 

 directly under the 

 outflow tube. 



As all viscosity de- 

 terminations should 

 be compared with 

 that of water at 25° C. the apparatus should be previously calibrated as 

 follows: The cup and outlet tube should first be scrupulously cleaned, 

 A piece of soft tissue paper is convenient for cleaning the latter. The 

 stopper is then inserted in the tube and the cup filled with water at 

 25° C.'to the top of the projections. The measuring cylinder should 

 be placed directly under the outflow tube so that the material, upon 

 flowing out, will not touch the sides, and the stopper may then be 

 removed. The time required both for 50 and 100 cubic centimeters 

 to run out should be ascertained by means of a stop watch and the 

 results so obtained should be checked a number of times. The time 

 required for 50 cubic centimeters of water should be about 1 1 seconds 

 and for 100 cubic centimeters about 22.8 seconds. 



Bituminous road materials are tested in the same manner as water 

 and the temperature at which the test is made is controlled by the 

 bath. The material should be brought to the desired temperature 







Fig. 4. — Englerviscosimeter. 



