16 BULLETIN 448, U. S. DEPABTMEli;'! OF AGEICULTUEE. 



with the similar solution obtained by the procedure outlined in section 8 and both 

 fractionated together. 



The normal hydrochloric acid solution is again partly neutralized by addition of 

 sodium hydroxid (to I'oui-th-normal or lessj and is shaken out with a mixture of 3 

 volumes carbon tetrachlorid and 1 volume dichlorhydrin to extract the lower sul- 

 phonated triphenylmethane dyes. These may be obtained in water solution again, 

 by washing out with water after adding more carbon tetrachlorid. 



Sec. 12. The acetic acid solution obtained by the procedm-e described in section 

 10 will contain the chief part of any monosulphonated monazo dyes present. Such 

 colors may be further fractionated, with amyl alcohol and normal sodiiun carbonate, 

 with ether and dilute hydrochloric acid, etc. 



The coloring matters of this gi'oup may appear in small proportion in the fractiona- 

 tion described in section 8, and obviously the similar solutions there described may be 

 combined with the acetic acid solution obtained as described in section 10. 



Sec. 13. The main part of the eosin dyes, and of unsulphonated water-soluble acid 

 colors in general, will be found in the sixty-fourth-normal sodium hydroxid solution 

 obtained by the extraction described in section 10. A large proportion of the natural 

 coloring substances also appear here. 



The eosin dyes may be fractionated between normal sodium hydroxid and amyl 

 alcohol or amyl alcohol gasoline mixture (3:1). 



The acid dyes also having basic tendencies, as Fluorescein (No. 510), Metanil 

 Yellow (No. 95), etc., differ from the others in being extracted from strongly acid solu- 

 tions in smaller amounts than from weakly acid solutions, and this property offers a 

 suitable means for their separation (pages 27-28) . These colors, as already pointed out, 

 mav be obtained, though in most cases in very small proportion, in the amyl alcohol 

 o-asoline solution obtained by the extraction described in section 8. 



Sec. 14. — The residue mentioned in section 10 is moistened with a small drop of 

 alcohol and then some ether and sixty -fourth-normal hydrochloric acid are added. 

 The mixtiu'e is pom'ed into a separatory funnel and is shaken. The aqueous layer is 

 drawn off, and if dyes coloring the aqueous solution were present, the ether is washed 

 a few times farther with the sixty-foujth-normal acid, to remove them. The acid 

 solution contains the rhodamins, perhaps also some of the basic azo colors. 



The ether solution if colored is now washed a few times with four-normal hydro- 

 chloric acid, the washings being neutralized at once and reserv^ed for treatment accord- 

 ing to section 15. 



The ether is finally washed a few times with water to remove acid; then it is taken to 

 dryness on the steam bath and the residue treated according to section 16. 



gj.(. ]^5 This group, consisting of oil-soluble colors, may be further separated by 



taking up the dye in gasoline or petroleum ether from the neutralized solution obtained 

 as described in section 14, and fractionating from this solvent with methyl alcohol, 70 

 per cent or above. (See pages 32-33.) Ortho-tolueneazo-/3-naphthylamin suffers de- 

 composition rather rapidly in strongly acid solutions. On the other hand, both it and 

 the lower benzene homologue, when their ether solutions are shaken with acid, are 

 extracted, but slowly, the amount of color removed from the ether depending on the 

 time of contact of the two layers. The substance in the ether layer would thus seem 

 to imdergo rearrangement before forming the water-soluble salt, but one or both forms 

 suffer complete decomposition by prolonged standing with the acid. 



Sec. 16.— The residue containing Sudans, etc., may be treated with measured quan- 

 tities of methyl alcohol, water, and sodium hydroxid in the proportions necessary to 

 bring the mixture to foui'th-normal alkalinity in 80 per cent alcohol; the solution then 

 may be shaken out with gasoline. Quinolin Yellow and a-naphthol derivatives 

 remain chiefly in the alkaline solvent. The petroleum ether is washed again, if neces- 

 sary, with the same mixture, then treated as described in section 17. 



