METHODS OF ANALYSIS FOR CERTIFIED COLORS. 217 



CALCIUM. 



Determine as given under Naphthol Yellow S, page 215. 



SULPHUR. 



Determine as given under Naphthol Yellow S, page 215. 

 NITROGEN (SEEKER AND MATHEWSON'S METHOD). 



Treat 2 grams of the color with 25 cc of a saturated solution of 

 sulphur dioxid and 1 gram of zinc dust and warm the mixture gently 

 until it becomes colorless. This should take place in from two to three 

 minutes, but if it does not add more sulphur dioxid solution in small 

 portions at a time until the color is destroyed. Then add 30 cc of con- 

 centrated sulphuric acid and 0.7 gram of mercuric oxid or its equiva- 

 lent of metallic mercury and digest the mixture, make alkaline, and 

 distil as directed on page 6, Bulletin 107, Revised, Bureau of Chemistry, 

 United States Department of Agriculture, under the Kjeldahl process. 



CRUDE CUMIDIN. 



Dissolve 20 grams of dye in 400 cc of hot water and pour the solu- 

 tion, a little at a time, into a reducing solution composed of 75 grams 

 of stannous chlorid dissolved in 180 cc of concentrated hydrochloric 

 acid. Heat the mixture on a steam bath until it is straw colored, 

 cool, add an excess of sodium hydroxid, and extract in a separatory 

 funnel with ether. Separate the ether layer and distil off the solvent 

 until the residue measures about 50 cc. Then cautiously heat over 

 the steam with constant agitation until the odor of ether disappears, 

 after which the last of the moisture is removed by introducing a few 

 pieces of solid caustic soda and allowing to stand. The residue con- 

 sists of crude cumidin and should boil above 220 C. Cumidin 

 nitrate is sparingly soluble in water. 



ORANGE I. 

 MOISTURE. 



Determine as given under Ponceau 3R, page 215. 



TOTAL INSOLUBLE MATTER 



Determine as given under Naphthol Yellow S, page 211. 



NONVOLATILE OR INORGANIC INSOLUBLE MATTER. 



Determine as given under Naphthol Yellow S, page 211. 



SODIUM CHLORID. 



Determine as given under Ponceau 3R, page 215. 



