Mercury thermometer dynamics

A mercury thermometer having first-order dynamics with a time constant of 60 s is placed in a bath at 308 K (35°C). After the thermometer reaches a steady state it is suddenly placed in a bath at 313 K (40° C) at / = 0 and left there for 60 s, after which it is immediately returned to the bath at 308 K (35°C). 

Figure 6 Apparatus for determination of vapour pressure by dynamic method, A, Monel boiler provided with central thermometer pocket B, aluminium tube-oven C, coupling linking metal connecting tube to glass D, mercury-filled manometer connected to oil-filled line leading to piston gauge E, glass valve with PTFE stem Fisher and Porter Company, U.S.A.) F, reservoir for introduction of the sample G,H, electrical heater windings K,L, control resistor windings, insulated by suitable wrappings from G and H M, platinum resistance thermometer N, connection to vacuum system...

The dynamic behavior is in agreement with the interpretation from the simple behavioral model as depicted in Fig. 1.5. The thermometer behaves like a first-order system with a mercury height which varies linearly with the temperature. 

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