10 BULLETIN 448, U. S. DEPARTMENT OF AGRICULTURE. 
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 fourth-normal or less) 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 procedure 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 sodium carbonate, 
with ether and dilute hydrochloric acid, etc. 
The coloring matters of this group 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, 
may be obtained, though in most cases in very small proportion, in the amyl alcohol 
gasoline 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 mixture is poured 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 further with the sixty-fourth-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 reserved 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. 
Sec 15. — 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 undergo 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 fourth-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. 
