Abstract: A flow-through cell has a body under which an ion-selective electrode is disposed. The side portion of the cell body is provided with a reference electrode. The cell body has a sample path with a crank form and also has a substantially horizontally extended path for a reference electrode solution. The crank path has a lower horizontal part, so that it is possible to suppress the undesirable flowing down of the reference electrode solution into the ion-selective electrode during an ion concentration measurement operation. The crank path has a upper horizontal part, which serve to suppress the undesirable flowing of the blood cells contained in the blood sample towards the path for the reference electrode solution. Furthermore, the crank path for the sample is designed to suppress the occurrence of bubbles in the path, with the previso that, if such bubbles should occur, these bubbles may be smoothly withdrawn.

Abstract: A pressure equilibrator has a slider received slidably in a pressure accumulation chamber and partitioning the chamber into two opposing sections, and a relief port formed in the inner side surface of the chamber. The slider is inserted into the pressure accumulation chamber with a minute gap left around the slider. Two gases are respectively introduced into the sections of the pressure accumulation chamber to be equilibrated in pressure. The gap provides passageways for connecting the respective sections of the pressure accumulation chamber with the relief port so as to discharge parts of the gases.