This is a modified version of the colorimeter devised by Jules Duboscq in Paris. E. Leitz, Inc., the American agents for the optical instruments manufactured by Ernst Leitz in Wetzlar, Germany, was selling this form by 1925 and describing it as a "Compensation Colorimeter and Hemoglobinometer involving the 'Buerker' Principle." Karl Buerker, the Director of the Physiological Institute at the University of Giessen, had published an account of a colorimeter with a "Huefner" prism in 1923. This prism, designed by Albrecht Huefner, brought the images of the two cups together in the eyepiece and insured that "both halves in the comparison field are of identical shade, obviating the minutest error which is so commonly found with colorimeters of other manufacturers."
This example is marked "Ernst Leitz / Wetzlar / No 255" and "Germany." New it cost $125. The Baker Laboratory of Chemistry at Cornell University donated it to the Smithsonian in 1960.
Ref.: E. Leitz, Inc., Leitz Microscopes (New York, 1929), p. 228.
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