Fig. 6.

Water TP cell in an ice bath contained in a silvered Dewar. A—platinum resistance thermometer; B—heavy black felt shield against ambient radiation; C—polyethylene tube for guiding the SPRT into the thermometer well; D—water vapor; E—borosilicate glass cell; F—water from the ice bath; G—thermometer well (precision bore); H—ice mantle; I—air-free water; J—aluminum bushing with internal taper at upper end to guide the SPRT into the close-fitting inner bore; K—polyurethane sponge; L—finely divided ice and water.