The magnetic diver differential microgasometer

The magnetic differential microgasometer described here is basically an equalarm torsion balance for measuring the reduced weight of submerged objects. The changes of buoyancy (ΔV_gx;ΔRW) are compensated for by the magnetic force acting on the same arm where the change has occurred (substitution method of weighing). Two ampullae, one with the sample and the other with the blank, are placed into the loops mounted at the ends of the arms. The gas volume and the geometry of the ampullae are practically equal. Therefore, the instrument is stable and fairly insensitive to changes of barometric pressure and temperature, and it can be used for gasometric measurements in an open flotation vessel. The applicability of the method for experiments where high blanks cannot be avoided was demonstrated by respiration measurements of multiplying cells and by measurements of cholinesterase activity of muscle end-plate samples.