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EXAMINATION OF BITUMINOUS ROAD MATERIALS, 25 
DIMETHYL SULPHATE TEST. 
EQUIPMENT. 
Same as specified under distillation test, and in addition: 3 10-cubic centimeter 
glass cylinders with ground-glass stoppers, graduated to 0.2 cubic centimeter. 
METHOD. 
The dimethyl sulphate test is employed to detect the presence of 
petroleum or asphalt products in tar. The pitch (above 300° ©.) 
obtained from the distillation test is used. This pitch, after beg 
cooled and weighed, is again distilled. Fractions are taken at 350° C. 
and 375° C. These fractions, together with the 270-300° C. fraction 
previously obtained, are separately stirred and, if necessary, heated 
to dissolve solids which may be present. 
Four cubie centimeters of distillate from each fraction are separately 
shaken with 6 cubic centimeters of dimethyi sulphate in a 10-cubic 
centimeter cylinder. After standing 30 minutes the resulting super- 
natant layer of msoluble oul, from the petroleum or asphalt, is read 
and calculated to its percentage by volume of the sample of distillate 
taken. The results are reported as follows: 
| Per cent | 
i : | of distillate 
Se Saree | Percent ; insoluble 
: SEES | of distillate. in 
| dimethyl ; 
,; Sulphate. | 
| 
OWN SON Ge = ere Sep Rise ee | 
300° to 350°C... pater eg a Fite ace a 
ts PORTER Cee is RE te On ee | 
USE OF DIMETHYL SULPHATE TEST. 
The dimethyl sulphate test is used only in cases where a mixture 
of petroleum or asphalt products with tar has been specified or is 
suspected. The test is mainly qualitative, but is valuable when as 
little as 3 per cent of petroleum or asphalt products are present in the 
tar. 
DETERMINATION OF BITUMEN SOLUBLE IN CARBON DISULPHIDE. 
EQUIPMENT. 
1 100 cubic centimeter Erlenmeyer flask. 
1 500 cubic centimeter flask with side neck for filtering under pressure. 
_1 rubber stopper with one hole. 
1 filter tube, 3.9 centimeters, inside diameter. 
1 platinum or porcelain Gooch crucible. 
a 1 piece of seamless rubber tubing, about 3 centimeters in diameter and 3 centimeters 
long. 
50 grams of long-fiber amphibole asbestos. 
