82 DEPARTMENT BULLETIN 1216, U. S. DEPT. OF AGRICULTURE 
Expansion chamber: To permit heating the thermometer at least 50° C. 
(90° F.) above highest temperature on scale. 
Filling above mercury: Nitrogen gas. 
Top finish : Glass ring. 
Graduation : All lines, figures, and letters clear cut and distinct. Each whole 
degree centigrade or Fahrenheit line to be longer than the remaining lines. 
Graduations to be numbered at each multiple of 2° C. or 5° F. 
Immersion : Total. 
Special marking : "A. S. T. M. low S. P.," a serial number and the manufac- 
turer'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 0.2° G. or 0.4° F. 
Assembly 
of .Apparatus. 
Proper Position 
of Ball. 
Fig. 33. — Apparatus for ring-and-ball method 
Standardization : The thermometer shall be standardized immersed in the 
testing bath to the top of the mercury column, at the ice point and at tempera- 
ture intervals of approximately 20° C. or 40° F. 
Case: The thermometer shall be supplied in a suitable case on which shall 
appear the marking : "A. S. T. M. low S. P., — 2° to +80° C," or "A. S. T. M. 
low S. P., +30° to +180° 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. 
