METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 85 
34. METHOD OF TEST FOR SPECIFIC VISCOSITY 
1. The viscosity of fluid bituminous road materials may be determined at 
any suitable temperature by means of the Engler viscosimeter. This appa- 
ratus is shown in Figure 34. and may be described as follows : a is a brass 
vessel for holding the material to be tested, and may be closed by the cover b. 
To the conical bottom of a is fitted a conical outflow tube, c. exactly 20 millime- 
ters long, with a diameter at the top of 2.9 millimeters and at the bottom of 
2.S millimeters. This tube can be closed and opened by the pointed, hard- 
wood stopper (7. Pointed metal projections are placed on 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 c is used to 
ascertain the temperature of the material to be tested. The vessel a is sur- 
rounded by a brass jacket, f. which holds the material used as a heating bath, 
either water or cottonseed oil, according to the temperature at which the test 
is to be made. A tripod, g. serves as a support for the apparatus and also 
carries a ring burner, h. by means of which the bath is directly heated. The 
measuring cylinder of 50 cubic centimeter capacity, which is sufficiently accurate 
tor wurk with road materials, is placed directly under the outflow tube. 
2. As all viscosity determinations 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 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 centimeters of 
water should be about 11 seconds. 
3. 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 and maintained there for at least 
three minutes before making the test. The results are expressed as specific 
viscosity compared with water at 25° C, as follows: 
. . o ^ Seconds for passage of 50 c. c. at A C. 
Specific viscosity at A C.=- — ^-^ 
Seconds for passage of oO c. c. of water at 2o C. 
55. METHOD OF TEST FOR WATER IN PETROLEUM 
PRODUCTS AND OTHER BITUMINOUS MATERIALS 
i A. S. T. M. standard method < Ji, serial designation D 95-27) 
1. This method of test determines water existing in a sample of bituminous 
material by distilling the sample with a volatile solvent. This method is 
suitable for a variety of materials but is especially applicable to petroleum, 
fuel oil. road oil. coal tar. water-gas tar. coke-oven tar, and other petroleum 
products or bituminous materials. 
APPARATUS 
2. The apparatus shall consist of a metal still or glass flask, heated by suit- 
able means and provided with a reflux condenser discharging into a trap con- 
nected to the still or flask. The trap serves to collect and measure the condensed 
water and to return the solvent to the still. 
The type of distilling apparatus used is not an essential feature of this 
method, but glass has been generally used for petroleum products and the metal 
still for road materials and tars. 
3. (a) The metal still (fig. 35, a) shall be a vertical cylindrical vessel, pref- 
erably of copper, having a faced flange at the top to which the head is tightly 
attached by means of a clamp. The head shall be of metal, preferably of brass 
or copper, and be provided with a tubulation 1 inch in inside diameter. 
(b) The glass flask (fig. 35, b) shall be of the short-neck, round-bottom type. 
made of well-annealed glass, having an approximate capacity of 500 cubic 
centimeters. 
