Chemical decomposition method

The plasma chemical decomposition method is based on rapid heating, decomposition and hydrolysis of fluoride compounds to obtain powdered oxides following interaction with water. Rakov and Teslenko [533] showed that the following hydrolysis equilibrium... 

Two arguments can he put forward in favour of wet chemical decomposition methods in open vessels, firstly, price, and, secondly, sample throughput. A wet decomposition can, if necessary, be performed with a beaker and a heating plate, whereas apparatus for modem high performance decompositions can cost as much as 25 000. With respect to sample throughput, the automatic wet digestion device can be used for up to 1 SO samples per hour for some materials. Such throughput cannot be realized by any other method. Some special cases exist that necessitate decomposition in open vessels (for instance, when the sample needs to be treated with perchloric acid). 

The PFC gas decomposition and removal method is classified into two methods combustion method and chemical decomposition method. 

The first experiments on the plasma chemical decomposition of fluoride solutions containing tantalum or niobium to obtain tantalum and niobium oxides were reported about fifteen years ago [524]. Subsequent publications were devoted to further development and expansion of the method for other refractory rare metals such as titanium and zirconium [525 - 532]. 

Niobium oxide obtained by plasma chemical decomposition is an ultra-fine powder with a specific surface area, as determined by the BET method, of about 20-30 m2/g. The estimated average particle size does not exceed 0.1 pm. 

Desizing by chemical decomposition is applicable to starch-based sizes. Since starch and its hydrophilic derivatives are soluble in water, it might be assumed that a simple alkaline rinse with surfactant would be sufficient to effect removal from the fibre. As is also the case with some other size polymers, however, once the starch solution has dried to a film on the fibre surface it is much more difficult to effect rehydration and dissolution. Thus controlled chemical degradation is required to disintegrate and solubilise the size film without damaging the cellulosic fibre. Enzymatic, oxidative and hydrolytic degradation methods can be used. 

Another method to control photoassisted transformations is to use molecules that may be excited under visible light (Equation 12.13), such as dye molecules. These molecules (denoted by the letter X in the following equations) are able to inject electrons into the conduction band of a catalyst (Equation 12.14). The cation radical formed under these conditions may undergo chemical decomposition, unless it regenerates in a period of time smaller than the period needed for its decomposition (Equation 12.15) [29]... 

Astaxanthin was detected at 480 nm. The chromatographic profiles of microencapsulated and free astaxanthin after eight weeks of storage are shown in Fig. 2.36. It was concluded from the results that the method is suitable for the study of the stability of miroencapsulated astaxanthin. The HPLC data proved that microencapculated as (ax an h tin did not suffer isomerization or chemical decomposition under the experimental conditions [79],... 

Remarks ideal instrument for labs with high throughput of similar samples. All methods of wet chemical decomposition can be performed... 

Yu, Z, Robinson, P., McGoldrick, P. 2001. An evaluation of methods for the chemical decomposition of geological materials for traoe element determination using ICP-MS. Geostandards Newsletter, 25, 199-217. 

Quantitative analysis of copolymers is relatively simple if one of the comonomers contains a readily determinable element or functional group. However, C,H elemental analyses are only of value when the difference between the carbon or hydrogen content of the two comonomers is sufficiently large. If the composition cannot be determined by elemental analysis or chemical means, the problem can be solved usually either by spectroscopic methods, for example, by UV measurements (e.g., styrene copolymers), by IR measurements (e.g., olefin copolymers), and by NMR measurements, or by gas chromatographic methods combined with mass spectroscopy after thermal or chemical decomposition of the samples. 

As described in Section 3.3.2.1 on heat sensitivity, thermoanalytical methods are sufficiently sensitive as an early indication of incipient chemical decomposition or chemical reaction, that is, stability and incompatibility. Some research papers discuss the use of differential thermal analysis (DTA) and differential scanning calorimetry (DSC) for this purpose [20-22]. 

Destruction of Basic LSt by Chemical Decomposition can be achieved by a method similar... 

A rational deduction of elemental abundance from solar and stellar spectra had to be based on quantum theory, and the necessary foundation was laid with the Indian physicist Meghnad Saha s theory of 1920. Saha, who as part of his postdoctoral work had stayed with Nernst in Berlin, combined Bohr s quantum theory of atoms with statistical thermodynamics and chemical equilibrium theory. Making an analogy between the thermal dissociation of molecules and the ionization of atoms, he carried the van t Hoff-Nernst theory of reaction-isochores over from the laboratory to the stars. Although his work clearly belonged to astrophysics, and not chemistry, it relied heavily on theoretical methods introduced by and associated with physical chemistry. This influence from physical chemistry, and probably from his stay with Nernst, is clear from his 1920 paper where he described ionization as a sort of chemical reaction, in which we have to substitute ionization for chemical decomposition. [81] The influence was even more evident in a second paper of 1922 where he extended his analysis. [82]... 

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