5.1

The thermometer must be free from any defects which might prevent it from operating normally, or which might lead to errors by the users.

5.2

The capillary tube must allow the mercury column to be seen clearly throughout its length, and the position of the top of the meniscus to be defined (preferably, it should be of the prismatic magnifying type).

The mercury column and scale must be clearly visible simultaneously.

5.3

The mercury must be sufficiently pure and dry

The bulb, capillary tube, and mercury must be sufficiently free from entrapped gas, debris and foreign bodies in order to ensure the correct functioning of the thermometer.

5.4

When the thermometer is heated slowly the mercury column must rise with an even movement, without appreciable jerks. After the thermometer has been heated to at least and then cooled to a temperature below minimum scale value, the mercury column must fall below the lowest numbered line when the mercury at the base of the bulb is subjected to an acceleration of .

5.5

The scale-bearing strip in an enclosed-scale thermometer must be fixed tightly against the capillary tube, an the method of fixing must prevent any displacement of one part with respect to the other.

The position of the strip with respect to the capillary tube must be clearly marked, so that any possible accidental relative displacement of the two parts can be easily detected1).

5.6

The protective sheath of an enclosed-scale thermometer must be free from moisture, mercury, debris or any foreign bodies.