Heat traditional methods

The more traditional methods of phenazine synthesis falling into the type A synthesis are altogether less satisfactory than the application of the Beirut reaction. Traditionally, Ris prepared phenazine in low yield by heating o-phenylenediamine and catechol in a sealed tube at 200 °C (1886CB2206) however, the method appears to be unsatisfactory at best and gives, in addition to phenazine, 5,10-dihydrophenazine in varying amounts (Scheme 53). Several variants of this procedure exist o-benzoquinone has been used in condensation with 0-phenylenediamine and yields as high as 35% have been reported, and 1,2,3,4-tetrahydrophenazine has been prepared by condensation of o-phenylenediamine with cyclohexane- 1,2-dione. 

An unusual method for the preparation of 3-(trifluoromethyl)-4-aryl-furazans 49a,b in 47-77% yield has been reported (99H627) (Scheme 19). Thus, dehydration of l,l,l-trifluoroalkane-2,3-dione dioximes 48a,b was accomplished on heating with silica gel. If, as in 48b, Ar was an electron-withdrawing moiety, the conversion proceeded more smoothly. The dehydration of the same dioximes using traditional methods failed. 

Nitric acid is also useful as an oxidant for the formation of sulphate from sulphones. Two such methods have been developed, firstly the established AOAC method which involves oxidation with a mixture of nitric acid and bromine221, and secondly the Carius method222. The latter is probably the oldest method used for the determination of sulphones as sulphate. This oxidation procedure involves heating the sulphone with concentrated nitric acid and sodium chloride at 280-300 °C in a sealed tube. The traditional method as described is prone to explosions. This problem may be alleviated by using less nitric acid whilst employing an oxygen atmosphere2 23,224. The Carius method is slower than the other oxidation methods described above but it usually yields the best results. 

A greater hindrance for paleoclimate studies, however, is that the traditional method required reduction in an all metal vacuum line at high temperature (in externally-heated nickel reaction vessels) with bromine pentafluoride (BrFs), a highly reactive gas (Clayton and Mayeda 1963). Handling this material in anything other than a dedicated geochemistry laboratory has proven extremely difficult and dangerous (Chivas 1984). 

The most obvious advantages are the reduction in effluents and the improved working atmosphere. The safety aspects have also been improved to a very large extent and the quality of the product in many cases is superior to that produced by the older methods. All forms of heat treatment are amenable to fluidized bed techniques, but austempering is the most cost effective, in spite of the nitrate bath method being less troublesome than other traditional methods. 

Sterilization by irradiation was introduced by mid-fifties. In about 20 years, it was fully operational. When compared with the traditional methods of sterilization such as using formaldehyde, ethylene oxide (a toxic gas), or heating in an autoclave, several advantages of irradiation may be noted (Artandi, 1977) ... 

By a traditional method, a- and /i-iononcs can be converted to ionene, catalyzed by HI along with small amounts of phosphorus. A cleaner cydization occurred by heating /i-ionone in water at 250 °C in the MBR [50]. In the workup the usual exhaustive washing procedures were unnecessary. Similarly, as mentioned above, carvacrol was prepared almost quantitatively, by isoaromatization of carvone in water at 250 °C for 10 min [47]. A conventional, literature method utilized acidic conditions, took a longer time and proceeded in lower conversion. The above examples show that elevated temperatures under neutral pH conditions can offer advantages over acidic (or basic) reagents at lower temperatures. 

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

The surface area of PSs can be measured by means of quantitative electron microscopy (EM) [49-51], knowing the sizes of particles and pores [51,52], wetting heat [7,53] measurements, etc. But, the most universal methods are based on adsorption measurements [51,53-55], corresponding to the traditional methods of pore size distribution measurements in the range 0.3 to 100 nm. 

Miller, K Auld, J., Jessup, E., Rhodes, A., and Ashton-Key, M. (1995) Antigen unmasking in formalin-fixed routinely processed paraffin wax-embedded sections by pressure cooking a comparison with microwave oven heating and traditional methods. Adv. Anat. Pathol. 2, 60-64. 

The traditional method for generating nanoparticles in mesoporous materials includes a wet impregnation process, followed by treatment with heat, reducing reagents or oxidation. This method could be applied to a lot of metals [43, 61] or metal oxides [50, 59], Other... 

The traditional method for the preparation of boron nitride is by the fusion of urea with boric acid in an atmosphere of ammonia at 750 °C.54 The product from these reactions is hexagonal boron nitride with a layer structure like that of graphite. Unlike graphite, it is colorless and is not an electronic conductor. Conversion of the hexagonal form to a cubic modification requires heating at 1,800 °C at 85,000 atmospheres pressure. 

Two key steps involved in the traditional methods are antiserum preparation and the agglutination tests. Sera for O determination are produced by immunization of rabbits with cultures that have been heated at 100°C for 2 h. Broth cultures or agar plate suspensions heated at 100°C for 1 h are used as antigens for typing. With these two procedures, bacterial agglutination is a very simple and sensitive method for qualitative O antigen determination. 

Blow moulding was adapted to making containers from plastics from traditional methods of blowing glass bottles. Essentially, the thermoplastic is heated... 

The thermodynamic approach considers micropores as elements of the structure of the system possessing excess (free) energy, hence, micropore formation processes are described in general terms of nonequilibrium thermodynamics, if no kinetic limitations appear. The applicability of the thermodynamic approach to description of micropore formation is very large, because this one is, in most cases, the result of fast chemical reactions and related heat/mass transfer processes. The thermodynamic description does not contradict to the fractal one because of reasons which are analyzed below in Sec. II. C but the nonequilibrium thermodynamic models are, in most cases, more strict and complete than the fractal ones, and the application of the fractal approach furnishes no additional information. If no polymerization takes place (that is right for most of processes of preparation of active carbons at high temperatures by pyrolysis or oxidation of primary organic materials), traditional methods of nonequilibrium thermodynamics (especially nonequilibrium statistical thermodynamics) are applicable. 

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