Indicator Properties of Dinitroaniline Azo Dyestuffs HENRYWENKER,616 Jackson Ave., Elizabeth, N, J. 2,CDinitroaniline -.,benzoyl H acid; color range red to blue,
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N A PREVIOUS article (I) the author described a new in-
dicator, 2,4-dinitroaniline-azo-l-naphthol-3,6-disulfonic acid, which he called nitrazine yellow. Since then many similar dyes have been investigated, using 2,4- and 2,6-dinitroaniline and their sulfonic acids as diazotable amines and 1- and 2-naphthol and their sulfonic acids as azo components. All couplings were made in dilute sulfuric acid solution. The results are shown in Table I. Comparison of these dyes indicates: 1. Only azo components with coupling-I-naphthol, and 1,6-, 1,7-, and 1,s-naphtholsu onic acids-give indicators of strong color contrast and relatively narrow pH range. 2. The 2,C position of the nitro groups of the diazo comonents is preferable to the 2,6-position as the former gives h e r and brighter, the latter redder and duller shades in alkaline solution and therefore less color contrast. 3. A few of the new dyes compare with nitrazine yellow in color intensity and contrast, but we inferior in solubility and narrowness of pH range.
pH range 5.8 t o 7.6.
2,4-Dinitro-l-naphthylamine-7-sulfonio acid + l-naphthol-6sulfonic acid; color range dull orange to greenish blue, pH range 5.6 t o 7.4.
Obviously no improvements can be expected by modifying the indicator molecule alonh lines as indicated by these three dyes. In preparing nitrazine yellow a red dye is always formed simultaneously, and can be separated from the indicator proper by repeated fractionated salting out, nitrazine yellow being precipitated first. Probably this red dye, which also turns blue in alkaline solution (pH range 9.6 to > 10) is the ortho azo dye, while nitrazine yellow is the para isomer. Because of the difficulty of completely reducing azo dyes which contain a nitro group in ortho position to the azo group-formation of triazoles-no experimental proof for this supposed isomerism can be brought so far. Concerning the nature of the intermolecular rearrangement which these dyestuffs undergo in acid and alkaline solution, respectively, it has been proved that the blue form of nitra-
Other dyes prepared in this connection are: 2,kDinitroaniline + H acid; color range red to blue, pH range 8.0 to > 10. TABLEI I. INDICATOR PROPERTIES 2.6-DINITROANILINB
2,4-DINITROANILINE-6SULFONIC ACID
2.6-DINITROANILINI'4-8ULFONIC ACID
1-NAPHTHOL
Dry Sulfuric aoid Water Aloohol Acid Alkali PH
Red-brown Blue Insoluble Slightly soluble Insoluble Blue 7.8 to 9.6 in alcoho
Orange Violet Insoluble Slightly soluble Yellow Violet 4.4 to 7.4 in aloohol 1-NAPHTHOL-4-BULFONIC
:&ria aoid Water Alcohol Acid Alkali PH
Dark red Blue Slightly soluble Soluble Orange Ph e 8 to >10
Dry Sulfuric acid Water Alcohol Acid Alkali PH
Red-brown Dull brown Slightly soluble E sluble Dull orange Blue 7.0 to 10.4
%uric acid Water Alcohol Acid Alkali PH
Red Purple Soluble Insoluble Yellow Bright blue 6.6 t o 8.6
Red-brown Pur le Sligftly soluble Very soluble Bright ellow Bright glue 5.2 to 8.2
Yellow Bri ht purple Sligjtly soluble Insoluble Blue yellow Pale
Dark red Dull red-brown Soluble Soluble Yellow Dull green 5.8 to 7.8
Red Dull red Soluble Soluble Dull yellow Dull wine red 6.4 to 8.0
Brown r 111 brown Suluble Soluble Dull orange Blue 6.6 to 9.0
Red-brown Dull brown Soluble Slightly soluble Dull orange
Bright yellow Bright purple Soluble Soluble Bright ellow Bright glue 3.8 to 7.4
Orange Bright purple Soluble Insoluble Bright yellow Violet 5.0 to 7.2
Could not be isolated
Brown Bright purple Soluble Slightly soluble Dull orange Blue-red 3.0 t o 6.8
Yellow Bright ur le Very sokbfe Soluble Yellow Blue, slightly green 5.8 to 8.4
Dull red Bright ur le Very sokbfe Insoluble Yellow Blue 6.4 t o 8.2
Could not be isolated
Red Bright pur le Very solubPe Insoluble B n ht yellow D U B violet 5.2 to 8.0
6.2 to 7.3
ACID
Red Red Slightly soluble Soluble Orange Blue-red >10 l-NAPHTHOL-6-BULFONlC ACID
Could not be isolated
Violet, .
6.0 t o 8.8
1-NAPHTHOL-6-BULFONIC A C I D
Red Bright purple Soluble Insoluble Dull orange Wine red 5.4 to 7.0 1-NAPHTHOL-7-BULBONIC
Dry Sulfurio acid Water Alcohol Acid Alkali PH
Brown Pur le Sligftly soluble Slightly soluble
Dry Sulfuric acid Water Alcohol Acid Alkali PH
Yellow Purple Slightly soluble Slightly soluble Bright ellow Bright glue 7.6 t o 10
Dry Sulfuric acid Water Alcohol Acid Alkali PH
Red Bright blue Soluble Insoluble Bright ellow Fright glue 6.0 to 7.0
Yellow - ....
Blue 6.6 to 8.6
ACID
Dark brown Bright purple Soluble Ver soluble Y el%w Purple 5.0 to 7.4 1-NAPHTHOL-8-SULFONIC
ACID
Yellow Bright purple Soluble Soluble Bright yellow Blue, slightly red 6.8 to 8.8 l-NAPHTEIOL-S,B-DIBULFONIC ACID
Red Bright pur le Very solub?e Insoluble Yellow Purple 5.4 to 7.4
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ANALYTICAL EDITION
January 15, 1935
41
TABLBI. (Continued) 2,6-DINITROANILINE 2-NAPHTHOL
Dry Sulfuric acid Water Alcohol Acid Alkali PH
Bri ht orange VinL
I&iible Very slightly soluble Yellow in alcohol Blue in alcohol
Bright red Red Insoluble Insoluble
..... ..... .....
2,4-DINITROANILINE-6BULFONIC ACID
2,6-DINITROANILINE4-BULFONIO ACID
Bri h t red viofet Very slightly soluble Insoluble Orange Blue 8.8 to >IO
Bright orange Blue-red Soluble Insoluble Orange Blue 8.4 to C10
Orange Orange
Insoluble Yellow Oreen 7.8 to 9.8
Orsnge Orange Very soluble Insoluble Orange Wine red 8.2 to 9.8
Could not be isolated
Could not be iaolated
R BALT
Bright red Bright urple Very soyuble Insoluble Red Dull violet
Bright red Bright red Soluble Insoluble
PH
>10
%uric acid Water Alcohol Acid Alkali PH
Bright red Orange Very soluble Insoluble Orange Dull violet >10
Could not be iaolated
%uric acid Water Aloohol Acid Alkali
Orange
Red 8.8 to >10
Very soluble
0 BALT
Bine yellow contains three sodium atoms. This salt can be isolated by precipitating the indicator from a strongly alkaline solution with alcohol; it forms a dark powder of metallic luster, is quite stable, can be dried a t 100" C., and has been analyzed. While in the dyes derived from 2,6-dinitroaniline it must be an ortho nitro group which becomes ionogen in alkaline
solution, it is an open question which of the two nitro groups assumes this function in the indicators derived from 2,4 dinitroaniline.
LITERATURE CITED ('1 Wenker*IN=*ENQ.
CaPM.* 26* 350 (1934)*
RSCEIVED August 14, 1934.
Baume-Purity-Moisture Tables for Corn Sirup W. R. FETZER AND J. W. EVANS, Union Starch and Refining Company, Granite City, Ill. Low purity 30 to 35 The moisture content of a corn sirup or corn Brewery use as "body sirups" of corn sirup are refined sugar for a given Baumk has beenfound dependent Regular Duritv 40 to 45 annually in the United Confectionery trade upon the purily of the sirup involved. Increasing States. Corn sirup is produced High purity 50 to 55 purity results in increasing dry substance for a Brewery and bakery trade from starch by acid hydrolysis given Baumk. in three purities-low, regular, The bulk of the sirup sold is of and high-and consists of dexThe dry substance values f o r corn sirup, as t r i n , m a l t o s e , and dextrose. regular or medium purity. found in several tables in use among the trade, In the mechanical separation Purity is defined within the inhave beenfound too high. A new table employing of starch from corn, a yield of 30 dustry as the amount of reducing purity as well as Baumi has been constructed to 33 pounds per bushel is obsugars expressed as dextrose on a for the entire range of the usual starch hydrolytic dry substance basis. As the actained. I n the subsequent hytual dry substance in corn sirup d r o l y s i s of starch, there is a products. is difficult to determine, the cuschemical gain, the amount deSeveral corn sirups and corn sugars from diftom in the industry has been to pending upon whether sirup or ferent refineries have been analyzed for dry sube x p r e s s t h e purity on a Brix sugar is produced. Thus, the stance, with results which indicate that for equal solids basis as a matter of conyield in d r y s u b s t a n c e of the Baumk and purity the moisture content is the same. venience, even though the Brix various products produced on solids are not the actual solids. the basis of the dry substance The term "purity" is necessary, as the same sirup is sold corn used became an important measure of the efficiency of a a t different gravities. I n selling, gravity is used as a measure refinery. It was soon found that the Brix solids could not be of the dry substance contained in the sirup, and will run from used for the measure of dry substance in corn sirup and sugar, 41" to 47" BB., being expressed a t 100" F. Sirups with a so special tables were constructed for the usual range of sirups gravity of 41" and 42' are more often termed "mixing sirups" produced, retaining the Brix solids for the basis of the purity and are largely used by manufacturers of mixed table sirups. determination. Each refinery either constructed a special Confectioners' sirup runs from 43" to 46" BB., the bulk being Baum6-moisture table or adopted one already in use a t another sold a t 43" BB., as this gravity represents the practical limit refinery. Once a table was in use, corrections became imat which this heavy viscous sirup may be handled economi- possible, as the management decreed that such a change would cally. In recent years considerable 42' BB. sirup has been render comparison with past factory performance impossible. sold to confectioners, as it is handled more easily in the piping If each factory was self-contained, this attitude might have systems which have been installed in candy factories. The been justified, but in selling sirups on the market, these purities produced by each refiner vary to a small degree, various moisture tables were given customers, who at once noticed that one table gave more dry substance for a given but the range and major use of the three types produced are:
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VER one billion pounds
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