Permanent red

Monoazo Pigments. In combination with other groups, the a2o linkage, —N=N—, imparts color to many dyes and pigments (see Azo Dyes). The simplest of these, ie, the Hansa yellows, toluidine reds, and naphthol reds, do not have the lightfastness and heat stabiUty required for plastics. Permanent YeUow FGL and Permanent Red 2B are stable enough for vinyls, polyethylene, polypropylene, and ceUulosics (11). Permanent Red 2B is available as the calcium, barium, or manganese salt. 

Permanent-gelb, n. permanent yellow, -rot, n. permanent red, red toner. -weUs, n. permanent white. 

After the end point, add 2.5 g of sodium fluoride, stir (or agitate) for 1 minute. Now introduce the standard manganese (II) sulphate solution from a burette in 1 mL portions until a permanent red colour is obtained note the exact volume added. Stir for 1 minute. Titrate the excess of manganese ion with EDTA until the colour changes to pure blue. 

Using a dropping pipette, add LOOM sodium hydroxide (NaOH) drop by drop to the acid solution, stirring after each drop, until 1 drop of base causes the solution to remain a permanent red color. 

Observing and Inferring What is the significance of the permanent red color change in step 6 ... 

Dyeing with madder yielded brilliant, permanent reds. When the dye was used in conjunction with different mordants, however, it provided a variety of hues, as listed in Table 95. Madder was also used for the preparation of red lakes (see Textbox 20), as for example, that applied to colored Greek terracotta statuettes (Abrahams and Edelstein 1967 Farnsworth 1951). For many generations and up to the present time madder has also enjoyed popularity in the Middle East for its medicinal properties. Madder has been identified in human bones buried in Qumran at the Dead Sea in Israel. People living at Qumran apparently believed that madder had medicinal and even magic properties, and drank a concoction of madder as a beverage (Steckoll et al. 1971). 

Permanent Red 2B, Barium Salt, pigment for plastics, 7 366t... 

Permanent Red 2B, Calcium Salt, pigment for plastics, 7 366t Permanent set, of fibers, 11 184 Permanent setting, in wool processing, 26 387-388... 

Cool the dish, add 25mL of water and heat with, stirring to almost boiling, then filter thru No 2 Whatman paper. Cool the soln to RT and titrate to the first permanent red color with 0.01N Ag nitrate in the presence of five drops of saturated K chromate indicator... 

Titrate with the std 0.15N ferric ammonium sulfate soln to the first permanent red coloration Conduct a blank detn using the same reagents and in the same quantities as above, but no sample... 

The change in color of a pH indicator is not permanent. Red cabbage juice brought to a pH of 4 turns red. This same solution brought to a pH of 8 turns green and then red again as it is brought back to a pH of 4. 

Quantitative Determination. — Dissolve 1 gm. of hydroxyl-amine hydrochloride in 30 cc. of water, and titrate the solution with normal potassium hydroxide to permanent redness, using plienolphthalein as indicator. 

Quantitative Determination. - Dissolve 0.2 gm. of sodium rhhiridr in l(M) cc.. of water, add a few drops of potassium chmmiite solution, and titrate, with dc.emormal silver nitrate Hiiluliou until a permanent red precipitate, just Ixigins to form. 

Figure 2. Example of endogenous alkaline phosphatase in ileum stained with Permanent Red.

Permanent Red 2B (Barium Red 2B, PR 48 1, Cl No. 15865 1 Calcium Red 2B, PR 48 2, Cl No. 15865 2 Manganese Red 2B, PR 48 4, Cl No. 15865 4). Discovered by DuPont in the early 1920s the permanent red 2B pigments are azo reds prepared from coupling diazotized l-amino-3-chloro-4-methyl benzene sulfonic acid onto 3-hydroxy-2-naphthoic acid (BON).The barium salt is characterized by a clean, yellow hue as compared to the bluer calcium salt. The barium salt has a poorer lightfastness and weaker tinting strength however the barium salt will provide better heat stability in certain polymer systems. The calcium salt provides the most widely used blue-shade red. 

Pigment scarlet is a clean, blue-shade red with acceptable heat fastness as compared to the economics of the product. Temperatures up to a maximum of 500°F (260°C) can be tolerated for short periods during the processing of the colorant. The marginal economics associated with the use of this pigment is all that restricts its more widespread acceptance within the plastics industry. The pigment is suitable as a colorant for rubber and finds some use in vinyl plastics and cellulosics. Pigment scarlet shows less tendency toward plate out as compared to permanent red 2B when molded in plasticized PVC applications. 

Technical Observations. Permanent red 2G (lithol fast orange R) is, like Hansa yellow, a valuable pigment color having outstanding fastness to light and very good oil and spirit fastness. 

The main body of the solution of the nitro compound is then neutralized with soda ash to the point giving a permanent red coloration, and heated to 60-65°C. The calculated amount of concentrated hydrosulfide solution is added slowly with stirring, and the mixture is held at 60-65° for 3 hours. Enough salt is then added to make the solution 10 per cent with respect to salt, and the solution is cooled with stirring. The precipitated dye is filtered off, washed with 15 per cent salt solution until the washings are colorless, pressed out, and dried at 90°. The yield of alizarin saphirol B is about 105 grams. 

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