Abstract: A method for precisely and accurately determining the volume of a test liquid aliquot which can be used to calibrate a liquid delivery device. The method is particularly useful for determining the volume of an aliquot of a test liquid which is complex or non-aqueous, or is both complex and non-aqueous. The test-stock mixture contains at least the test liquid and a stock solution including a first dye, the first dye having absorbance characteristics which are measurably distinguishable from the absorbance characteristics of a second dye. The test-stock mixture is mixed with a diluent including the second dye to form a sample solution to be used to measure absorbances of the first dye and the second dye. The volume of the test-stock mixture aliquot is calculated by using a formula based on the Beer-Lambert law which incorporates the measured absorbance values and a dilution characteristic of the test-stock mixture.

Abstract: A comparitive colorimeter for use in the field which simultaneously compares the color densities of two liquid samples and designates the degree of difference. The apparatus includes two major subsystems, optical and electronic. The optical subsystem is designed to provide identical light beams through both the sample and standard solutions and to minimize the effect which imperfect sample tubes have on the output. The electronic subsystem includes a log conversion and differential amplifier circuit for generating a difference signal representative of the difference between the optical densities of the sample and standard solutions. The difference signal is evaluated by a comparative circuit consisting of a resistive chain having a plurality of node voltages and hex inverters connected to the node voltages. The hex inverters drive a series of LED indicator lights to designate the relative degree of difference between the optical densities of the sample and standard.