84 DEPARTMENT BULLETIN 1216, U. S. DEPT. OF AGRICULTURE 
Filling above mercury : Nitrogen gas. 
Top finish : Glass ring. 
Graduation: All lines, figures, and letters clear cut and distinct. Each 
whole degree centigrade line or the first and each succeeding 5° F. line to be 
longer than the remaining lines. Graduations to be numbered at each multiple 
of 5° C. or 10° F. 
Immersion : Total. 
Special marking : "A. S. T. M. high S. P.," a serial number and the manu- 
facturer's name or trade-mark shall be etched on the thermometer. 
Scale error: The error at any point of the scale when the thermometer is 
standardized as provided below shall not exceed 0.3° C. or 0.5° F. 
Standardization: The thermometer shall be standardized, immersed in the 
testing bath to the top of the mercury column, at intervals of approximately 
40° C. or 70° F. 
a 
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Fig. 34. — Engler viscosimeter 
Case: The thermometer shall be supplied in a suitable case on which shall 
appear the marking: "A. S. T. M. high S. P., 30 to 160° C," or "A. S. T. M. 
high S. P., 85 to 320° F.," according to the type of thermometer. 
Note. — For the purpose of interpreting these specifications the following definitions 
apply : The total length is the over-all length of the finished instrument. The diameter 
is that measured with a ring gauge. The length of the bulb is the distance from the 
bottom of the bulb to the beginning of the enamel backing. The top of the thermometer 
is the top of the finished instrument. 
PRECAUTIONS 
9. The use of freshly boiled distilled water is essential, as otherwise air 
bubbles may form on the specimen and effect the accuracy of the results. Rigid 
adherence to the prescribed rate of heating is absolutely essential in order to 
secure accuracy of results. 
A ^heet of paper placed on the bottom of the glass vessel and conveniently 
weighted will prevent the bituminous material from sticking to the glass vessel, 
thereby saving considerable time and trouble in cleaning. 
ACCURACY 
10. The limit of accuracy of the test is ±0.5° C. (0.9° F.). 
