The clinical estimation of hemoglobin, judging by the variety of instruments made and used for that purpose, is still a source of dissatisfaction, especially in a general hospital where such determinations are made in large numbers daily.
The criteria for any instrument to be used in the clinical laboratory are, first, sufficient accuracy, and, second, simple and expeditious operation. To be perfectly satisfactory for clinical purposes, an instrument need not be absolutely accurate. But simplicity of operation is the sine qua non of any apparatus destined to become of routine use in a busy clinic.
Various methods of measuring hemoglobin have their adherents, but the Sahli1 modification of Gower's instrument, in spite of its shortcomings, is probably the most widely used. The principle involved in Sahli's method is simple: A measured quantity of blood is treated in a calibrated tube with tenth-normal hydrochloric acid, in order to change its