Chapter 21 Temperature Measurement C. Hagart-Alexander 21.1 TemperaTure and heaT 21.1.1 application Considerations Temperature is one of the most frequently used process measurements. Almost all chemical processes and reactions are temperature dependent. in chemical plants, temperature is not infrequently the only indication of the progress of a process. Where the temperature is critical to the reaction, a considerable loss of product may result from incorrect temperatures. in some cases, loss of control of temperature can result in catastrophic plant failure, with the attendant damage and possible loss of life. other heat-related phenomena. These are described in the following sections. 21.1.2.1 Temperature The first recorded temperature measurement was carried out by Galileo at the end of the 16th century. His thermometer depended on the expansion of air. Some form of scale was attached to his apparatus, for he mentions "degrees of heat" in his records. As with any other measurement, it is necessary to have agreed and standardized units of measurement. in the case