A critical temperature indicator (2) is provided utilizing the volume reduction characteristics of organic compounds as they undergo a change from the liquid state to the solid state. The bulb (4) and a portion of the capillary tube (6) of a thermometer-like structure contains a colorless organic compound (10). Another organic compound (12) saturated with a dye, which compound (12) has a solidification temperature lower than that of the colorless compound (10) and which is miscible with the colorless compound (10), is located in the capillary tube (6) and separated from the colorless compound (10) by a solid, movable plug or a liquid (14) which is immiscible with either the colorless or the dyed compound (10, 12). The volume of the colorless compound (10) upon solidification is less than the volume of the bulb (4) so that the separating plug or liquid (14) and at least a portion of the dyed compound (12) are drawn into the bulb (4) upon solidification. The dyed compound (12) then mixes with the colorless compound (10) to provide a visual indication that the colorless compound (10) has solidified.
临界温度指示器(2)是利用有机化合物从液态变为固态时体积缩小的特性而提供的。类似温度计结构的灯泡(4)和毛细管(6)的一部分含有无色有机化合物(10)。另一种饱和
染料的有机化合物(12)位于毛细管(6)中,其凝固温度低于无色化合物(10)的凝固温度,且可与无色化合物(10)混溶,该化合物(12)与无色化合物(10)之间由固体活动塞或液体(14)隔开,液体(14)与无色化合物(10、12)或染色化合物(10、12)均不可混溶。无色化合物(10)凝固后的体积小于灯泡(4)的体积,因此分离塞或液体(14)和至少一部分染色化合物(12)在凝固后被吸入灯泡(4)。染色化合物 (12) 然后与无色化合物 (10) 混合,以提供无色化合物 (10) 已凝固的视觉指示。