Pressure effects oxygen solubility

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

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. 

The effect of oxygen pressure on the solubilities of siderophile elements in silicate melt has been understood for many years due to metallurgical interest, and has been known to the geological community since early work of Newsom and Drake (1982, 1983) on tungsten and phosphorus. Although there was a brief exploration of the possibility of zero valence dissolution of nickel and possibly cobalt at low /o (Colson, 1992 ... 

At these pressures the solubility of nitrogen in the blood increases dramatically. Oxygen solubility increases as well, although its effect is less serious (O2 is 20% of air, N2 is 80%). As the diver quickly rises, the pressure decreases rapidly, and the nitrogen "boUs" out of the blood, stopping blood flow and impairing nerve transmission. The joints of the body lock in a bent position, hence the name of the condition the bends. 

Normally, oxygen solubility is strongly dependent on (1) the amount of dissolved electrolyte salt s) (decreases at higher concentration of electrolyte), (2) temperature (decreases at higher temperatures), and (3) pressure (increases at higher pressure). We will give some detailed discussion about these factors and their effects on the O2 solubility in the following subsections. 

Tromans D. Oxygen solubility modeling in inorganic solutions concentration, temperature and pressure effects. Hydrometallurgy 1998 50(3) 279-96. 

The oxygen transfer rate (OTR) from air to culture is a critical parameter in these microbial cultivation processes, and the effects of different conditions of agitation and aeration on the production of decalactones were investigated with Y. lipolytica [128]. OTR depends on the fluid s physical properties, temperature, pressure, solution composition, agitation, oxygen superficial gas velocity, and the configuration of the reactor [129]. OTR in a system is a function of the volumetric mass transfer coefficient (kid) and the oxygen solubility in the medium. For a specific bioreactor and medium, it is possible to increase and, consequently,... 

Rosenfel d" considers that SO2 can act as a depolariser of the cathodic process. However, this effect has only been demonstrated with much higher levels of SO2 (0-5%) than are found in the atmosphere (Table 2.4) and the importance of this action of SO2 has yet to be proved for practical environments. However, SO2 is 1 300 times more soluble than O2 in water" and therefore its concentration in solution may be considerably greater than would be expected from partial pressure considerations. This high solubility would make it a more effective cathode reactant than dissolved oxygen even though its concentration in the atmosphere is comparatively small. 

Assuming the randomness factor is about the same, the gas with the larger heat effect (favoring dissolving) should have the higher solubility. The measured solubilities at one atmosphere pressure and 20°C of oxygen and nitrous oxide in water are, respectively, 02, 1.4 X 10-3 mole/liter and N20, 27 X 10-3 mole/liter, consistent with our prediction.. 

We have now found that replacing water in the melt by methanol leads to large increases in pyridine solubility of product from the treatment, even without tetralin addition. In this paper we characterize the effects of temperature, time, hydrogen pressure, reaction stoichiometry, and addition of various inorganic and organic additives. Because oxygen removal Present Address Chevron Research Co., Box 1627, Richmond, CA 94804. 

In contrast, when boron trifluoride etherate is substituted for the free boron trifluoride, only a trace of the hydrocarbon is formed, even after weeks of reaction.143 The unique effectiveness of boron trifluoride gas in promoting these reductions is believed to be due to several factors, including the ability of the coordinatively unsaturated boron center to rapidly and tightly coordinate with oxygen centers and to the thermodynamically favorable creation of a Si-F bond.1 A slight pressure of boron trifluoride gas must be maintained over the surface of the solution throughout the reaction because boron trifluoride has only limited solubility in the weakly coordinating dichloromethane solvent. 

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