Deterioration with decomposition

Table II summarizes the major types of wood deterioration and the causal organisms. The following discussion deals with deterioration without cell wall decomposition the bulk of the chapter deals with deterioration with decomposition of cell walls.

Riboflavin occurs as a yellow to orange-yellow, crystalline powder. When dry, it is not affected by diffused light, but when in solution, light induces deterioration. It melts at about 280° with decomposition, and its saturated solution is neutral to litmus. One gram dissolves in 3000 to about 20,000 mL of water, the variations being due to differences in the internal crystalline structure. It is less soluble in alcohol than in water. It is insoluble in ether and in chloroform, but it is very soluble in dilute solutions of alkalies. 

A white, hygroscopic, crystalline or amorphous powder. Aqueous solutions containing 10% or more deteriorate rapidly on storage. M.p. about 205°, with decomposition. 

Colourless crystals or white or very pale yellow crystalline powder. Solutions, especially when made alkaline, deteriorate rapidly in air. M.p. about 190°, with decomposition. 

A yellow or orange-yellow, crystalline powder. M.p. about 280°, with decomposition. Solutions deteriorate on exposure to light. Soluble 1 in 3000 to 1 in 20 000 of water, the variation in solubility being due to the variation in the internal crystalline structure practically insoluble in ethanol, acetone, chloroform, and ether very soluble in dilute solutions of alkali hydroxides. 

Pentaeiythritol Tetranitrate. Specification-grade pentaerythritol tetranitrate (PETN) can be stored up to 18 months at 65°C without significant deterioration. However, many materials have been found to be incompatible with PETN and the presence of as Htfle as 0.01% occluded acid or alkah greatly accelerates decomposition. The decomposition of PETN is autocatalytic with reported kinetic constants oi E = 196.6 kJ/mol (47 kcal/mol) and Z = 6.31 x 10 . The decomposition products of PETN at 210°C in wt % are 47.7 NO, 21.0 CO, 11.8 NO2, 9.5 N2O, 6.3 CO2, 2.0 H2, and 1.6... 

The relative abundance of neutral SiH and H2 species have been measured as a function of power, pressure, flow rate, and dilution. For low power levels, eg, 5 W, up to 50% of the SiH gas is dissociated and the percentage increases to 80% for a power of 50 W. The decomposition of SiH gas proceeds more readily with lower flow rates. These observations, coupled with infrared (ir) measurements performed on the films, suggest that deposition under conditions in which the silane gas is not entirely decomposed leads to a majority of SiH units, whereas those deposited under conditions in which silane is strongly dissociated contain a majority of dihydride units leading to a deterioration of the semiconductor. Also, when the dwell time of SiH in the plasma region increases, the resultant film exhibits a pronounced peak at 2090 cm from the ir spectra corresponding to S1H2 inclusion. 

Succinic anhydride is stabilized against the deteriorative effects of heat by the addition of small amounts (0.5 wt %) of boric acid (27), the presence of which also decreases the formation of the dilactone of gamma ketopimelic acid (28). Compared with argon, CO2 has an inhibiting effect on the thermal decomposition of succinic acid, whereas air has an accelerating effect (29,30). 

Calcium hexacyanoferrate (II) (IIH2O) [ 13821 -08-4] M 490.3. Recrystd three times from conductivity H2O and air dried to constant weight over partially dehydrated salt. [Trans Faraday Soc 45 855 1949.] Alternatively the Ca salt can be purified by pptn with absolute EtOH in the cold (to avoid oxidation) from an air-free saturated aqueous soln. The pure lemon yellow crystals are centrifuged, dried in a vacuum desiccator first over dry charcoal for 24h, then over partly dehydrated salt and stored in a dark glass stoppered bottle. No deterioration occurred after 18 months. No trace of Na, K or NH4 ions could be detected in the salt from the residue after decomposition of the salt with cone H2SO4. Analyses indicate 1 Imols of H2O per mol of salt. The solubility in H2O is 36.45g (24.9 ) and 64.7g (44.7 ) per lOOg of solution. [J Chem Soc 50 1926.]... 

Struxine, C2iH3(,04N2, obtained by Schaefer from deteriorated nux-vomica seeds in about 0-1 per cent, yield, is regarded as a decomposition product of strychnine or brucine. It forms rhombic crystals from alcohol, is colourless, but becomes yellow on exposure to light and chars at 250°. It yields normal and acid salts, the latter only from excess of acid. With sulphuric acid it gives no coloration, but addition of potassium dichromate produces a yellow colour changing to green. 

Replication avoids the problem of sample deterioration in the instrument, but it is destructive in that reaction of the material cannot be continued after the replica has been prepared. Transitory features cannot be detected unless a series of preparations are examined corresponding to increasing progress of the reaction considered. The textures of replicas have been shown [220] to be in satisfactory agreement with those of the original surface as viewed in the scanning electron microscope. The uses and interpretations of observations made through sample replication procedures are illustrated in the studies of decomposition of metal carboxyl-ates by Brown and co-workers [97,221—223]. 

At another level, certain KBS approaches provide the mechanisms for decomposing complex interpretation problems into a set of smaller, distributed and localized interpretations. Decomposition into smaller, more constrained interpretation problems is necessary to maintain the performance of any one interpreter and it makes it possible to apply different interpretation approaches to subparts of the problem. It is well recognized that scale-up is a problem for all of the interpretation approaches described. With increases in the number of input variables, potential output conclusions, complexity of subprocess interactions, and the spatial and temporal distribution of effects, the rapidity, accuracy, and resolution of interpretations can deteriorate dramatically. Furthermore, difficulties in construction, verification, and maintenance can prohibit successful implementation. 

Samples of pure N-ethylallenimine and other allenimines have been stored at 0° for well over a year with no significant deterioration. Caution N-Alkylallenimines, even as dilute solutions in aqueous ethanol, are rapidly destroyed by acid>5 Therefore concentrated solutions of N-alkylallenimines should not be allowed to come in contact with acid because of the possibilities of violent decomposition. 

The reaction is thought to proceed with the dissociation of CT followed by release of the extra charge of the mthenium complex by dissociating a proton from the alkyhdene hgand. Such an exchange in itself does not lead to the decomposition of the alkyhdene complex. Nevertheless, both the formation of the charged species, both the intermediate existence of the carbyne complex (Scheme 9.5) may open new ways to the deterioration of the ROMP catalysts. 

The formation of free radicals after lipid oxidation is known to play a key role in the deterioration of meat flavor 8, 23), Since proteins constitute a major portion of the muscle s composition, the relationship between chemically active radical species and decomposition of food flavor proteins and peptides needs to be studied in detail. Data has been presented showing the correlation of proteins with flavor (Figures 5 and 6). Data is now presented showing how soluble meat proteins change in an environment where free radicals are induced by a free-radical oxidation generating system or FROG (Figure 10). 

---