of EC Hailed iiales ComnraeoL 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 35. 



H. W. WILEY, Chief of Bureau. 



REPORT ON COLORS: THE SOLUBILITY AND EXTRACTION OF COLORS 

 AND THE COLOR REACTIONS OF DYED FIBER AND OF AQUEOUS 

 AND SULPHURIC-ACID SOLUTIONS. 



By H. M. LOOMIS, 



Chemist, Pennsylvania Department of Agriculture, cooperating with the referee on colors, 

 Association of Official Agricultural Chemists. 



INTRODUCTION. 



The subject of food colors is so extensive, and so little, compara- 

 tively, has been accomplished in the field, that the reports of the 

 referees in charge of these investigations have been confined to pre- 

 liminary or tentative work, such for example as that reported in Cir- 

 cular 25 of this Bureau, by Mr. W. G. Berry, under the title " Color- 

 ing Matters for Foodstuffs and Methods for their Detection." The 

 present paper, submitted as a subreport at the 1906 convention of the 

 Association of Official Agricultural Chemists, it is thought will be of 

 considerable value, for reference, to those working along these lines, 

 although the results are, of course, only approximate, and will doubt- 

 less be improved upon by further work. 



Respectfully, H. W. WILEY, 



Chief of Bureau, 



Secretary, Association of Official Agricultural Chemists. 

 Approved: 



JAMES WILSON, 



Secretary of Agriculture. 



WASHINGTON, D. C., January 10, 1907. 



PLAN OF THE EXPERIMENTS. 



The tables given in this report show the result of experimental 



work done on various coloring matters. Most of the coal tar colors 



used were obtained direct from the manufacturers or agents, to whom 



grateful acknowledgment is due. The names of these firms and the 



3522 No. 3507 



