60 
BULLETIN 1216, U. S. DEPARTMENT OF AGRICULTURE. 
by the pointed hardwood stopper d. Pointed metal projections 
are placed od the inside of a at equal distances from the bottom 
and serve for measuring the charge of material, which is 240 
cubic centimeters. The thermometer e is used to ascertain the 
temperature Of the material to he tested. The vessel a is sur- 
rounded by a brass jacket, /. which holds the material used as a 
heating hath, either water or cottonseed oil. according to the 
temperature :it which the test is to he made. A tripod, g, serves 
as a support lor the apparatus and also carries a ring burner. //. 
by means of which the bath is directly heated. The measuring 
cylinder of oil cubic centimeter capacity, which is sufficiently 
accurate for work with road materials, is placed directly under 
the outflow tube. 
Method of test. As all viscosity determinations should be compared with that 
of water at 25° ('., the apparatus should be previously calibrated 
as follows: The cup and outlet tube should first be scrupulously 
y— 
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^ 
4. — Engler viscosimeter. 
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 thai the material, upon flowing out, will not touch the 
sides, and the stopper may then be removed. The time required 
for 50 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 centi- 
meters of water Should be about 11 seconds. 
Bituminous road materials are tested in the same manner as 
water, and the temperature at which the test is made is con- 
trolled by the bath. The material should be brought to the 
desired temperature and maintained there for at least three 
minutes before making the test. The results are expressed as 
specific viscosity compared with water at 25° <'.. ;is follows: 
Specific viscosity at .1° C. = 
seconds for passage of 50 cubic centimeters at A C. 
seconds for passage of ;">0 cubic centimeters of water at 25° C. 
