LIQUID HYDROMETER FOR MEASURING DENSITY OF FLUID WHICH IS WITHIN SPECIFIED RANGE WHILE COEFFICIENT OF HEAT EXPANSION THEREOF VARIES WITHIN THIS RANGE

摘要

For measuring the density of fluids whose densities lie within a predetermined range and whose coefficients of thermal expansion vary within this range, a stem hydrometer has a lower body volume which extends up to the lowest marking on the density scale and is immersed when the hydrometer is buoyant in a fluid at the highest part of the density range, a scale volume which extends between the lowest and highest markings on the density scale and is immersed with the body volume when the hydrometer is buoyant in a fluid at the lowest part of the density range, and a stem volume above the highest scale marking. The body volume has a coefficient of expansion substantially equal to that of the fluid at the highest part of the range, and the scale volume is comprised of material such that the coefficient of expansion of the combined body volume and scale volume is substantially equal to that of the fluid at the lowest part of the range. The total mass of the hydrometer takes into account the apparent additional mass resulting from surface tension of the fluid. For fluids whose coefficients of expansion change disproportionately with density, combinations of materials may be used in the scale volume so as to vary the coefficient of expansion along the scale volume in keeping with disproportional changes in that of the fluid.