CONTENTS. 7 



Page. 



XV. Guides in determining degree of purity and cleanliness 192 



XVI. Analyses of certified lots of permitted colors, 1909-10 198 



Tabulation of results 198 



Comparison of analyses made in 1907 201 



Conformity of analytical data with theoretical composition 202 



Arsenic determinations on 86 batches 204 



Suggested requirements for certified colors 205 



XVH. Methods of analysis used in testing colors for certification 210 



Introduction 210 



Naphthol Yellow S 211 



Ponceau 3R 215 



Orange 1 217 



Amaranth 220 



Light Green S F Yellowish 221 



Erythrosin 222 



Indigo disulphoacid 224 



XVm. Addenda 225 



Additional examination of coal-tar dyes 225 



Supplementary list of trade names of coal-tar colors 227 



XIX. Index of authorities quoted 227 



ILLUSTRATION 



Page. 

 FIG. 1. Apparatus used in the determination of arsenic 213 



