Abstract: This specification describes a new analyzer for the determination of total hemoglobin; percent oxyhemoglobin, deoxyhemoglobin, methmoglobin, sulfhemoglobin; and oxygen capacity in a micro sample (5 to 10 .mu.l) of hole human blood. The essential components of the analyzer are (1) a cuvette in which simultaneous measurements of PO.sub.2 (by an oxygen electrode) and absorbance (by a dual wavelength optical system) are made, (2) an automatic pump system for filling and emptying the cuvette, (3) an equilibrating tonometer to equilibrate the reagent with air or another gas phase, (4) electronic circuits for the measurement of light intensity and oxygen pressure, (5) an analogue computer, and (6) a printer. Other essential parts of the invention are (a) original procedures and (b) ad hoc developed physico-chemical equations.