Detailed Procedures

TM 9-6685-202-14

4-5. Detailed Procedures

a. Checking the Level of Mercury.

As long as the barometer is operating properly and the accuracy is within limits

specified in table 1-1, the mercury level need not be checked. When there is reason to suspect that mercury has been

added or removed from the barometer, the amount of mercury should be checked. It should read 0.1 mm. If it does not,

add or remove mercury as specified in paragraph 4-5b. Prior to checking the amount of mercury, the barometer must be

completely prepared for use as specified in paragraph 3-5.

b. Adding or Removing Mercury.

WARNING

Mercury vapors are dangerous. Mercury must be handled with care in a well-ventilated room.

Wash hands before handling food or cigarettes. Do not touch the mercury as oil from the skin

will contaminate it.

(1) Type A-1

(a) Prepare the barometer for use as specified in paragraph 3-5.

(b) Open cistern and barometer tube to atmospheric pressure and leave valves open.

(c) Remove the cistern nipple.

(d) Fill barometer with triple-distilled mercury until barometer indicates 0.1 mm. On the type A-1

barometer, the temperature and gravity indexes must be set for the existing conditions.

NOTE

It is usually better practice to overfill the barometer slightly, then skim off the excess to adjust to

zero.

(e) Use filtering flask MS-306066-3, rubber stopper ZZ-S-751, pipet 7913319, and tygon tubing

connected to the vacuum pump as shown in figure 4-1 to remove excess mercury from the cistern.

MI (C) 6685-202-14-4-1

Figure 4-1. Removal of mercury.

4-5