Dyestuffs raising

Pure samples are best prepd by the methylation of acetanilide or benzanilide to the N-methyl compds followed by acid hyd. It has been prepd commercially by the action of methyl ale on aniline in an autoclave under press and by the action of methyl amine on halobenzenes. For a summary of prepns see Refs 6 9. It may be separated from aniline and dime thy laniline by treatment of the mixt with benzenesulfonyl chloride. Dimethylamline fails to react and is extd out with dil acid. Aniline forms benzenesulfonanilide which is acidic and is removed by washing with dil base, leaving the N-methylbenzenesulfonanilide. Purified N-methylaniline is obtd by acid hyd (Ref 8). N-Methylaniline is used as an additive to raise the octane no of motor fuels (Ref 6), as a dyestuff intermediate (Ref 3), in the prepn of Tetryl (see below), and in the prepn of Methylcentralite (Encycl, Vol 2, C137-R)... 

Transfering of these results to an optimum dyeing process starting temperature should be 90°C to obtain an uniform dyestuff uptake and then raising up the temperature to get a completely dyed PET-fiber. 

Peter Griess, 1858.—Diazo compounds were discovered and first prepared by Peter Griess in 1858. The historical method used by him is the same in general as is now used widely in dyestuff manufacture. It has already been described and consists in the action of nitrous acid on an aromatic primary amine, e.g., aniline. When this reaction takes place, at ordinary or slightly raised temperatures, the same products are obtained as with aliphatic primary amines, viz., the hydroxyl compound of the hydrocarbon radical, free nitrogen and water. 

If, finally, the temperature of the reaction between sulphuric acid and alizarin blue be raised to 200° to 210°, or if alizarin green is heated to the same temperature with concentrated sulphuric acid, a third dyestuff. Alizarin Indigo-blue, is obtained. This body is a trioxyalizarin-blue. The commercial products are pastes which contain the bisulphite compounds. The shades produced in dyeing are sufficiently indicated by the names, being a dull indigo-blue and a dull bluish green respectively. The best results are obtained with chromium mordants. 

Method 2 The dye liquor is made up with 10 to 15 per cent of Glauber s salt crystals and 3 to 5 per cent of acetic acid (30 per cent). The temperature is raised to 40°C (105°F) and the goods are entered and, if possible, run for 10 to 20 minutes to equalize their pH. The dye is then added and the liquor is raised to the boil over a period of 45 minutes. Boiling is continued, and after 40 to 45 minutes exhaustion may be completed by slowly adding a further 1 to 3 per cent of acetic acid (30 per cent), 1 per cent of sulphuric acid 168°Tw(98 per cent), or 1 per cent of formic acid (85 per cent). This method would be used for dyes of the type in Table 15.5 and, if further additions of dyestuffs of this class are necessary to correct the shade, the liquor should be cooled. 

The method of dyeing which was used in the earlier times after the introduction of this class was to scour the wool and then to run it in a dye-bath containing 8 per cent (of the weight of the wool) of sulphuric acid, and 10 to 20 per cent of Glauber s salt at 60 C (140°F) for 15 minutes. The dyestuff, which had previously been dissolved, was then added through a strainer, after which the liquor was raised from 60°C (140°F) to the boil over a period of 30 minutes, and boiling was continued for 1 to 1J hours. 

When dyeing in a yarn package machine the dyestuff solution is added at 40°C (104°F) and, whilst the liquor is in circulation, the temperature is gradually raised to that recommended for the application of the dyes. The required quantities of sulphide and soda ash are dissolved separately, filtered, and entered into the machine gradually over a period of 20 to 30 minutes, after which exhaustion may be completed slowly, adding 15 to 25 per cent of common salt according to the shade. 

Wool can be dyed with Remazol dyes in the following way (Bohnert, loc. cit.). The dye liquor is made up with the dyestuff, 5 per cent of anhydrous Glauber s salt, and 4 per cent of sulphuric acid (96 per cent). The goods are entered at 40 C (104 F) and the temperature is raised to 60°C (140°F), over a period of 30 minutes, at which temperature it is maintained for 10 minutes before raising to the boil and dyeing continues at the boil for 1 hour. Polyamide fibres can be dyed in a similar manner and a strongly acid liquor is recommended for acrylonitriles. 

Even before the formal establishment of the three-party cartel, a united front of European and American producers had been formed against Japan. In October 1928, a half year after the effectuation of the Saito-Waibel Agreement, most Western producers simultaneously raised the export prices to Japan of all kinds of dyestuffs by a uniform 5 percent. This concerted action was proposed by LG. Farben and was followed by Swiss and American companies. In fact, Swiss companies were at first opposed to this action, partly for the technical reason that the different export prices of each company s products made it difficult to raise prices uniformly. A more important reason for their initial opposition was that the Swiss companies were afraid that Japanese companies, especially Nihon Senryo, in an attempt to dominate the Japanese market, would not follow the Western companies price increases. The fear of the Swiss producers became a reality Japanese firms did not follow suit. As a result, while the market share of the three-party cartel fell, that of the Japanese firms rose. Moreover, Japanese exports, mainly to the Chinese and other East Asian markets, exceeded 1,000 tons.30... 

Accordingly, from 1915 to the time of U.S. entry into the war, a reluctant expansion of German direct investment in the United States occurred. No new monies came in, albeit there were American profits that could be reinvested. The output of Bayer s Rensselaer plant spurted upward. The Hoechst plant in Newark raised production Metz acquired a half interest in the Central Dyestuffs and Chemical Company in 1915, which hiked its once minimal output. The Cassella Co. organized a new U.S. subsidiary— Century Color Co.—to begin manufacture under Cassella s familiar C.C.C. trademark (the trademark it had used for imports). U.S. dyestuff production, which had been 2.5 million in 1914, by 1917 soared to 57.8 million. The general price index had risen, but nowhere near this extent. A substantial part of the expansion in dyestuff output was by German subsidiaries in the United States. 

Alkali ferricyanides oxidize acid solutions of diethylaniline and other aromatic amines, as well as certain monoazo dyestuffs a change of color results and ferrocyanide is formed. This reversible redox reaction, proceeds very slowly and incompletely. However, if the ferrocyanide ions are removed as insoluble white zinc ferrocyanide, the oxidation proceeds rapidly. This acceleration is a result of raising the oxidation potential of ferricyanide ions through removal of ferrocyanide ions. The white zinc ferrocyanide is deeply tinted by adsorption of the colored quinoidal oxidation products of the amines, and thus affords a sensitive test for zinc. The test is especially useful in the presence of chromium and aluminum. It can also be used in other instances provided no other cations are present, which form colored precipitates with potassium ferrocyanide (Co+, Ni+, Fe+, Mn+ , Cu+ ). Traces of iron, which in practice are always to be reckoned with, do not interfere with the zinc test. Anions which oxidize the amines must be absent, e.g., permanganate, chromate, vanadate, persulfate, iodate. 

Perhaps the most convincing evidence of the colloidal nature of dyestuffs is given by the ultramicroscopic observations of Raehlmann, Michaelis, Hober, and others. These investigators have demonstrated that solutions of dyestuffs are sometimes filled with ultramicrons even when the liquid becomes colorless because of the great dilution. In confirmation of this view are the experiments of Krafft J which show that many of these salts such as Methyl Violet raise the boiling point of water correspondingly less than that of alcohol. 

Sulfuric acid is used for a variety of other purposes in the chemical industry. For example, it is the usual acid catalyst for the conversion of cyclohexanone oxime to caprolactam, used for making nylon. It is used for making hydrochloric acid from salt via the Mannheim process. Much H2SO4 is used in petroleum refining, for example as a catalyst for the reaction of isobutane with isobutylene to give isooctane, a compound that raises the octane rating of gasoline (petrol). Sulfuric acid is also important in the manufacture of dyestuffs solutions and is the "acid" in lead-acid (car) batteries. 

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