Technical observability

Technical Observations. In large scale production, quantities of benzene up to 1200 kilograms are sulfonated at one time. The gypsum is usually separated from the liquid by means of rotary filters similar to those used in soda manufacture. The specific gravity of the sodium salt solution is about 8-10° Be, and after concentration, about 25° Be (temperature 100°C.). 

Technical Observations. A whole series of altyl and phenyl ethers in the benzene series (also in the naphthalene and anthraquinone series) can be prepared in an analogous manner. While anhydrous methylate gives satisfactory results in the case of nitroanisole, there are other cases (e.g., dinitroanisole from dinitrochloro-benzene) where it is betSr to use caustic potash, the small water content having no deleterious efFect. Moreover, better reswts are often obtained if onb 90 per cent of the calculated quantity of alkali is used. 

Technical Observations. Dinitrochlorobenzene is manufactured on a very large scale, and is used in the preparation of sulfur black T (q.v.) and other important dyes. It is, moreover, the starting material for a whole series of condensation products made by replacing the very labile chlorine atom by basic and other residues. Thus, it is easy to prepare dinitroaniline and dinitrophenol, as well as picric acid and dinitroanisole, from dinitrochlorobenzene. The accompanying formulas show only a small part of the reactions actually used (also see Table V). 

Technical Observations. Sulfonations of this pe are carried out on a large scale in kettles provided with jackets through which either steam or cooling water can be circulated as desired. The reaction mixtures often become quite hot, and the operations must be conducted carefully so that dangerous overheating and explosion are avoided. Salting out is done in wooden vats, and the precipitate... 

Technical Observations. In large scale operations, involving volumes of 4000 to 5000 liters, the crystallization of 2,2 -benzidinedisulfonic acid requires at least 3 days. In order to obtain rapid cooling, lead coils, through which cold water is circidated, are installed in the wooden vats. The sulfonic acid must be diazotized indirectly because of its insolubility. It is dissolved in the required amount of water and soda, the neutral solution is mixed with sodium nitrite, and the mixture is allowed to flow in a thin stream into hydrochloric or sulfuric acid. 

Technical Observations. Michler s ketone and its homologs are important starting materials for the preparation of valuable triphenylmethane dyes such as Victoria blue B and Victoria pure blue BO. 

Technical Observations. Not only the autoclave proper, but also the cover, must be enameled. Traces of iron or copper reduce the yield of diphenylamine by as much as 30 to 50 per cent, and cause resinification. The hydrochloric acid extraction is carried out in wooden vats and the distillation with superheated steam is done in apparatus such as that shown in Figure 24. Modem devices are available for producing the superheated steam. It is possible to carry over nearly one part of diphenylamine wiUi one part of water at 230°. 

Technical Observations. In large scale operations, the distillation is carried out using either coil condensers, surrounded by warm water to prevent stoppage, or ordinary condensers supplied with warm water. 

Technical Observations. Large scale preparations use tannin solutions which are obtained by countercurrent extraction of the tannin-containing material with... 

Technical Observations. The process described above is the best and least expensive. There is, however, another method which is analftgous to the preparation of -naphthol. Sodium naphthalene-a-sulfonate is fused with caustic soda at 290° (not to exceed 300°). The sulfonation is carried out at 80-90°, and the product is salted out in as concentrated a solution as possible. The sulfonate can also be isolated by removing the excess acid with lime or chalk, treating with soda, and evaporating to obtain the product. The sulfonate, thus obtained, can be used in the fusion without further purification, but the resulting a-naphthol is impure. 

Technical Observations. The sulfonation of naphthalene is carried out in huge cast iron kettles holding 1000 to 3000 liters. Heating is done either directly with generator gas or by means of a steam jacket (double wall) (Figure 31) which must withstand at least 6 atmospheres in order that the required temperature of 174° can be attained. 

Technical Observations. Naphthalenetetraearboxylie aeid is obtained most easily — analogously to phthalic acid — by oxidation of the corresponding higher ring system, pyrene. Instead of first chlorinating the pyrene, it can be oxidized by dichromate and sulfuric acid to form pyrenequinone (mixture of the 3,8 and 3,10 quinones) and this can then be oxidized further to naphthalenetetraearboxylie acid by chloride of lime in the presence of lime, according to the reaction ... 

Technical Observations. Indantlirene red 5 GK is formed by benzoylation of 1,4-diaminoanthraquinone, and indanthrene yellow GK by benzoylation ot the 1,5 isomer. 

Technical Observations. Acid orange A is one of the most widely used monoazo dyes because of its low cost and bright color. In large scale preparations, the coupling reaction is done in huge pitchpine vats having a capacity of 15,000 liters or more, or in concrete vats measuring up to 40 meters across and lined with refractory tile. 

Technical Observations. The dyes described above have largely replaced the analogous dyes from chromotropic acid (l,8-dihydroxynaphthalene-3,6-disulfonic acid). They are cheaper and more stable to light. 

Technical Observations. The manufacture of pyrazolone dyes is relatively simple. The arylhydrazine condensations are usually run in enameled vessels to minimize losses of expensive materials. Nothing particularly new is involved in the diazotization and coupling reactions. 

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. 

Technical Observations. The preparation of naphthylamine black D can be done in various ways. Many industrial chemists prefer to salt out the diazo compound of the monoazo dye and filter it off to purify it. This has the advantage of removing unchanged o-naphthylamine and preventing the formation, in the final product, of the insoluble dye (wliich is not fast to rubbing) ... 

Technical Observations. The cotton black described above is the most widely used direct black in the dye industry. It is used in dyeing all organic materials, such as cotton, half-wool, leather, etc. The dye is prepared in the largest azo dye instal-... 

Technical Observations. Auramine is the most important basic yellow and is highly valued because of the extraordinarily pure tints it produces. Manufacture of the dye is done in oil heated vessels, and the heating must be very carefully... 

Technical Observations. Malachite green is still used in large quantities for coloring tin-weighted silk, wool, and paper. Pure compound shades are obtained inexpensively by using it in mixture with other dyes, but the tints are of only moderate fastness. The dye is also used in silk and cotton printing, but does not fulfill the modern demands for fastness properties so its use in these fields is declining. 

Technical Observations. Industrial preparations are carried out in enameled iron vessels with lead-tube reflux condensers. The preparation starting with 40 kilograms of gallamide requires about 12 hours. 

Naphthol yellow S, 151 Naphthsultone, 187, 217 a-Naphthylamine, 176 diazotization, 245, 260 technical observations, 178 y3-Naphthylamine, 54, 203 diazotization, 246 Naphthylamine black D, 277 l-Naphthylamine-2,4-disulfonic add, 80, 85, 178... 

Partial condensers, 24, 341 Partial reduction, 79, 113 Patent blues, 301 Permanent red 2G, 267 Phenanthrene, 1 Phenol, 51, 86 from chlorobenzene, 76, 88 technical observations, Phenolphthalein paper, 395 Phenols, separation, 30 Phend-o-svdfonic acid, 51 Phenol-m-sulfonic acid, 144,145... 

Technical Observations. Chlorobenzene is an important intermediate in the preparation of a whole series of other compounds (see Section 6 and Tables 1 to 5). It is produced in batches of 2000 kilograms or more in cast iron kettles equipped with agitators and reflux condensers. 

Technical Observations. In large scale operations, the aniline is distilled with steam which is already saturated with aniline. This is done by feeding the steam kettle with the waste water from the steam distillation process. In the Weiler-Ter... 

Technical Observations. The procedure is different in large scale operations. As soon as the reaction is ended, the excess ammonia is blown out through a condensing system (water), and the autoclave contents, in which all of the nitroaniline remains dissolved at 150°, is put through a strong iron filter press. The nitroaniline is given no opportunity to crystallize out, but is poured directly into cold water, whereupon it crystallizes in finely divided form. This is highly desirable because it can then be diazotized smoothly in the cold. 

Technical Observations. The nitrophenylhydrazines are used in preparing nitrophenylpyrazolones (page 129) which, after reduction of the nitro group to amino, are valuable components for substantive azo dyes. They can be diazotized and coupled on the fiber, or after treated with formaldehyde. ... 

Technical Observations. Reactions of this type are carried out most satisfactorily in lead lined iron kettles, and it is important that no other metal come in contact with the liquid. A few milligrams of copper or iron prevents the formation of even traces of the desired products. The dinitrobenzenesulfonic acid, as well as the final m-phenylenediaminesulfonic acid, is not filtered in a filter press, but is... 

Technical Observations. Phenylmethylpyrazolonesulfonic acid is used, for example, in the preparation of fast light yellow G (page 265). Phenylmethylpyra-zolone itself (from phenylhydrazine and acetoacetic ester) and maiw of its derivatives are valuable components for the preparation of yellow azo eyes which, for the most part, are characterized by very high stability. 

Technical Observations. Heating of the large autoclaves used in industrial preparations requires from 4 to 6 hours and must be done very carefully. When a temperature of about 190°C. is reached, the pressure increases rapidly from 10 to 30 atmospheres. At the end of the reaction, the excess methyl alconol, along with the ether formed, is blown out and the vapor is condensed. Splitting of the quaternary ammonium base is carried out in large kettles, using 3(X)0 to 50(X) kilograms of dimethylaniline. 

Technical Observations. Acetoacetanilide is used in the prmaration of important insoluble pigment colors which are known under the trade name, Hansa yellow (see page 266). 

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