. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Contribution from the Bureau of Chemistry CARL L. ALSBERG, Chief. J^.^"^W(L Washington, D. C. PROFESSIONAL PAPER February 15, 1917 SEPARATION AND IDENTIFICATION OF FOOD- COLORING SUBSTANCES. By W. E. Mathewson, Assistant Chemist. CONTENTS. Page Introduction 1 General statements concerning reagents used in color analysis 2 Preliminarj' treatment of food products 4 Page. Separation and purification of coloring sub- stances 8 Identification of coloring substances 35 INTRODUCTION. The scheme of analysis of dyes descri
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Contribution from the Bureau of Chemistry CARL L. ALSBERG, Chief. J^.^"^W(L Washington, D. C. PROFESSIONAL PAPER February 15, 1917 SEPARATION AND IDENTIFICATION OF FOOD- COLORING SUBSTANCES. By W. E. Mathewson, Assistant Chemist. CONTENTS. Page Introduction 1 General statements concerning reagents used in color analysis 2 Preliminarj' treatment of food products 4 Page. Separation and purification of coloring sub- stances 8 Identification of coloring substances 35 INTRODUCTION. The scheme of analysis of dyes described in this bulletin embrace about 130 chemical individuals. This number comprises practically ail those coal-tar colors (except a few entirely obsolete nitro dyes) which have been mentioned in the hterature as having been found in food products, and those mentioned as being suitable for the coloring of foods. A number of dyes which are typical represen- tatives of certain classes and which exemplify in a general way the analytical properties of certain groups, also have been included. No process for the analysis of dyes can be made so complete as to take into accoiuit all possible colors and combinations of colors; never- thrless the analyst should be prepared for as many as possible of the cases arising. It is especially difficult to take the newer colors into consideration, but, fortunately, at the present time these are very littl(! used in food products. The scheme- of separation d(!scribed is designed to meet actual con- ditions, one of which is the relatively more frequent occurrence of the eight colors the use of whicli in food is ])ermitt(Hl by the United States Department of Agricultuni' Amaranth, Pom^eau 3 K, Ery- • Food laspoctlon decisions Nos. 70 and IM. NoTB.—This bulletin will bo of interest chiefly to chemists engaged in food analysis. *-Uiill 44S~J7 1. Please note that these images are extracted from scanned page images that may have been digitally en
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