It is essential that the instruments be used in the manner prescribed if true temperatures are to be ascertained. The following are some terms that should be understood and adhered to when true temperatures are to be obtained. Thermometer is immersed into medium up to the point of reading. Thermometer is immersed up to immersion line or to depth inscribed on the back of the thermometer. It is most important to position the thermometer exactly as outlined in the method.
Any deviation can cause erroneous indications.
The largest single cause for the failure of precision thermometers in the lab is due to separated mercury columns. This can occur in transit or in the lab. The life of the instrument can be greatly extended if the following procedures are rigidly employed. Other methods may cause damage to the thermometer. Do not cool the stem or mercury column.