Effect of temperature and oxygen

Much has been written about the effects of processing, temperature, and storage conditions on the stability of ascorbic acid in citrus juices. On the other hand, little is known about the stability of folic acid under similar conditions. Chen and Cooper (72) studied the effects of temperature and oxygen and ascorbic acid on the thermal degradation of folic acid, and they reported that ascorbic acid increased the stability of the terra-... 

Airas S., Leppanen M., Kukkoncn J.V.K. (2008) Effects of temperature and oxygen concentration in sediment toxicity testing. Ecotoxicology and Environmental Safety 70(3) 475 182. 

Effects of temperature and oxygen concentration on oxidative deterioration during storage of crude sunflower oils, obtained by pressing and solvent extraction, were studied (11). Extracted oil showed a higher oxidative stability than pressed oil. 

Thermal stabilizers and antioxidants. These additives are used to protect the polymer against the effects of temperature and oxygen during processing. Free-radical scavengers such as hindered phenols and aromatic amines are typically added for this purpose. 

FIGURE 11.4. The effect of temperature and oxygen concentration on fouling rate (Illinois feed)... 

Dionigi C.P. and Ingram D.A. (1994) Effects of temperature and oxygen concentration on geosmin production by Streptomyces tendae and Penicillium expansum. J. Agric. Food Chem., 42, 143-145. 

Figure 22. Effect of temperature and oxygen Figure 23. Effect of temperature and oxygen...

The effect of plasticizers and temperature on the permeabiUty of small molecules in a typical vinyUdene chloride copolymer has been studied thoroughly. The oxygen permeabiUty doubles with the addition of about 1.7 parts per hundred resin (phr) of common plasticizers, or a temperature increase of 8°C (91). The effects of temperature and plasticizer on the permeabiUty are shown in Figure 4. The moisture (water) vapor transmission rate (MVTR or WVTR) doubles with the addition of about 3.5 phr of common plasticizers (92). The dependence of the WVTR on temperature is a Htde more comphcated. WVTR is commonly reported at a constant difference in relative humidity and not at a constant partial pressure difference. WVTR is a mixed term that increases with increasing temperature because both the fundamental permeabiUty and the fundamental partial pressure at constant relative humidity increase. Carbon dioxide permeabiUty doubles with the addition of about 1.8 phr of common plasticizers, or a temperature increase of 7°C (93). 

PERMANENT GASES Table 3 lists the permeabilities of oxygen [7782-44-7] nitrogen [7727-37-9] and carbon dioxide [124-38-9] for selected barrier and nonbarrier polymers at 20°C and 75% rh. The effect of temperature and humidity are discussed later. For many polymers the permeabihties of nitrogen, oxygen, and carbon dioxide are in the ratio 1 4 14. 

Vollertsen, J., M. do C. Almeida, and T. Hvitved-Jacobsen (1999), Effects of temperature and dissolved oxygen on hydrolysis of sewer solids, Water Res., 33(14), 3119-3126. 

The effect of temperature and [H+] on the oxygen exchange was studied for the W(IV) system by simple pH manipulation as was the case for the Re(V) mentioned above. However, here the pH had to be varied around high values (12-14) to attain the slow isotopic exchange conditions. The kinetic results were treated similarly to those of the Re(V) and are listed, together with the activation parameters, in Table V. 

Romanek CS, Grossman EL, Morse JW (1992) Carbon isotopic fractionation in synthetic aragonite and calcite Effects of temperature and precipitation rate. Geochim Cosmochim Acta 56 419-430 Rowe MW, Clayton RN, Mayeda TK (1994) Oxygen isotopes in separated components of Cl and CM meteorites. Geochim Cosmochim Acta 58 5341-5347... 

Hazen R. M. and Prewitt C. T. (1977). Effects of temperature and pressure on interatomic distances in oxygen-based minerals. Amer. Mineral, 62 309-315. 

The effects of temperature and concentration on direct and indirect oxidation kinetics of carbon monoxide were correlated with global models. In 1986, Helling and Tester found the oxidation of carbon monoxide to be globally first order in carbon monoxide and independent of oxygen concentration over the range investigated. 

While few things are absolutely insoluble, some solutes are much more soluble in a given solvent than others. The solubility of a solute is the amount of the solute that will dissolve in a given amount of solvent at a given temperature. For example, sodium chloride is quite soluble in water and has a solubility of 39.5 g per 100 mL of water at 25°C. We ll talk later about the effect of temperature on solubility. Oxygen, on the other hand, is not very soluble in water, with a solubility of 42 mg per 100 mL of water at 25°C and a pressure of 1 atm. We ll talk later about the effect of temperature and pressure on the solubility of gases. 

Figure 6.5. (a) Effect of temperature and (b) pressure on the amount of dissolved oxygen in water. (Data from Peavy, 1985). 

Therefore, more experimentation to determine the effects of water and oxygen upon the initial weight loss kinetics at low temperatures is necessary before we will be able to decide if weight loss thermal analysis is a viable technique to apply to the predicting of the service life of polyurethanes. 

The data in Fig. 1 show a drastic loss of selectivity with increasing reaction temperature and conversion, indicating a great sensitivity of benzaldehyde towards consecutive transformations, but do not allow discrimination between the effect of temperature and conversion of toluene and oxygen. Therefore, experiments were carried out at isotemperature and isoflow rate with different amounts of the catalyst or the 02/toluene ratio in the feed. The results are summarized in Figures 4A and 4B, respectively. 

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