60 
BULLETIN 949, U. S. DEPARTMENT OF AGRICULTURE. 
(c) Shield. — An asbestos shield of the form and approximate dimensions shown in 
figure 33 shall be used to protect the retort from air currents and to prevent radiation. 
This may be covered "with galvanized iron, as such an arrangement is more convenient 
and more permanent. 
(d) Receivers. — Erlenmeyer flasks of 50 to 100 c. c. capacity are the most convenient 
form. 
(e) Thermometer. — The thermometer shall conform to the following requirements. 
The thermometer shall be made of thermometric glass of a quality equivalent to 
suitable grades of Jena or Corning make. It shall be thoroughly annealed. It shall 
be filled above the mercury vrith inert gas which will not act chemically on or contami- 
nate the mercury. The pressure of the gas shall be sufficient to prevent separation of 
Thermometer 
Shield- 
Retort— 
Fig. 34.— Assembled apparatus for distillation test. 
the mercury column at all temperatures of the scale. There shall be a reservoir above 
the final graduation large enough so that the pressure will not become excessive at the 
highest temperature. The thermometer shall be finished at the top with a small glass 
ring or button suitable for attaching a tag. Each thermometer shall have for identi- 
fication the maker"s name, a serial number, and the letters "A. S. T. M. distillation. ' ? 
The thermometer shall be graduated from 0° to 400° C. at intervals of 1° C. E very- 
fifth graduation shall be longer than the intermediate ones, and every tenth gradua- 
tion beginning at zero shall be numbered. The graduation marks and numbers shall 
be clear-cut and distinct. 
The thermometer shall conform to the following dimensions: 
Mm. 
Total length, maximum 385 
Diameter of stem (permissible variation, 0.5 mm. ) 7 
Diameter of bulb, minimum I shall not exceed diameter of stem) 5 
Length of bulb (permissible variation, 2.5 mm.) 12. 5 
Distance, 0° to bottom of bulb I permissible variation, 5 mm.) 30 
Distance, to 400° (permissible variation, 10 mm.) .- 295 
