iT? BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
duce three sulphonic acid groups into the molecule without burning 
or charring the mass. Undersulphonation results in the production — 
of guinea green B; oversulphonation results in the breaking down of | 
the molecule. | 
Light green S F yellowish is a reddish-brown powder. It dis- 
solves in water to form a green solution, which, upon the addition of 
hydrochloric acid, turns yellowish-brown and then gradually fades. , 
Upon the addition of sodium hydroxide the aqueous solution is 
almost completely decolorized, yielding a dull violet precipitate. It 
is decolorized by a hot solution of alkalis and alkali carbonates. 
With concentrated sulphuric acid it forms a yellow solution, which, 
when diluted with water, turns green. 
The methods of examination and the maximum percentages of 
impurities tolerated are listed in Table 10, which also shows the 
analytical data to be incorporated in the foundation and supplemental 
affidavits (70). 
TABLE 10.—Specifications for light green S F yellowish 
eee 
olerance | Minimum Method of 
Component (ratio to pure| tolerance analysis 
coal-tar dye) 
Per cent Per cent Page 
MVITOISTIING = 28 = tes es Sk ett cacy Se oa en re epee ae emen LON O ese ee nee es 14. 
Insoluble matter: 
Ova ee ec eme k ee S oe Se ee eee es es elke ae as Be 15. 
INfonwolatile to 5.2 be Bh a Be a eh ee ND da 5s, ee ee car De 15: 
Sodiim-chlonid@s2 at eeee es Ae ee ee ee BiOo > ee Se re 15165 
Sodmimssulphiatecs st. 2 es sso a at eS She Se ee eae BiO.. <v/cceeee Bene 17. 
Ui IAbe el aSM =e ee Oe eee ee eto ee (CS ebay Got) (eee eke eee 2 18. 
Sodtumasinicoloreert-i2 soc oe sete eee ie ‘Theoretical: (2. 2< 22 18. 
Ee aM OLAS site oa ot Ce eee sre terete Nones ie 2-232 19. 
Waleimele. - = ast Se See een A ee ge eee ee nes OsSe Ss Le ae ee eee 19. 
Mragmes tims -<sS se Gi Ae ee ae SE Se re ee oe Br Sota ite fers 19. 
PATENT: 9s US tea oo i Si a hale ie Ee fd ete eh 19. 
MOT = ee cee Se ek SS ce Pe es te ee et ee) Hes Saree eee ore Oe 19. 
PATSOTIIC ASA Sagat. ne ek pe ee eRe ee eed ee Ce eee 5 (QODI4 s). Seen Feces 21,28: 
Ether extractives: 
TS UU "| be ee ae ee a Oe os Se es ee eS (1)\g = eed ees oe ee 23 
Ailicaarigks Meee cos obo iy ARR US RRR oC eee (¢) rn eeede weer y 23. 4 
TNC G EOE AS - EE A Se ey GT ae Er ae eee 8 (¢) eee eee 24. 
RY G) Fil [ies pe ee eee es ee NC me gee Sm SE are PGs Wee Ne eal ES ae ane see ee ee ee 24, 
Sulphurancolors 22-2223 Sk eee ee Theoretieal:-|-.2-<-..-2- 24, 
COlomaCId ee, = oe eee eS EN Se a a ee ea een ae Tish 4e25% 
PILE COA aLAIMOVe #2 ee Co aN a ee SLE ee oor pe ee el ee 82.0 | 26. 
Subsidiary dyes (to be calculated as guinea green B, unless S08 eee Sen 29. 
the identity of the extraneous dye or dyes is definitely 
known, in which case the known dye or dyes must be 
reported as individuals). 
1 Although no limit is here defined, a statement of the percentage found by analysis must be incor- 
porated in the foundation and supplemental affidavits (70). 
INDIGOTINE 
Indigotine (C,,H,N,O,S,Na,), or sodium indigo disulphonate, the- 
sodium salt of the disulphonic acid of indigo (14, 71), is prepared by 
sulphonating indigo (26, 27, 35). Because of its more homogeneous 
composition, it is better to use synthetic indigo rather than the nat- 
ural product for the manufacture of indigotine. Indigo of high purity 
honk be used, and care should be taken that the sulphonation pro- 
ceeds to the production of the disulphonic acid only. } 
Indigotine, a blue-brown or red-brown powder, dissolves in water — 
to form a blue solution. On adding hydrochloric acid, the aqueous ~ 
solution becomes bluish-violet; further dilution with water restores — 
