Solubility of gas in metal

For interstitial solid solutions, too, the criteria used historically for the degree of solid solubility relates to elastic and electronic interactions. Experimentally observed maximum interstitial solubilities of H, B, C and N in Pd are inversely proportional to the sum of the s and p electrons, and hence are controlled by the valence electron concentration. Thus the electronic interactions dominate the 

The slope is, for a specific system, given by the enthalpy and entropy of solution of hydrogen in the metal in other words by the energetics of the following reaction 

The relationship between the concentration of hydrogen in the metal and the partial pressure of hydrogen is now 

---

The diagrams which have just been described are of only limited value because the presence of an alloying element in solution in the iron influences the thermodynamic behaviour of the solute. Thus it is well known that the solubility of gases in metals at constant pressure is changed by addition of alloying elements and since this is only another way of saying that the activity coefficient of the gas atoms in the solution has been changed, we... 

The solubilities of gases in solid metals are much lower than liquid metals. Figure 10.18 shows the solubility of hydrogen in copper and copper-aluminum alloys. Because of the lower solubility in the solid, gas bubbles are released at the liquid-solid interface as the metal freezes. With long dendrites the gas bubbles are trapped and the result is gas porosity. 

Solubility of Gases in Platinum.—The solubility of hydrogen in platinum has been studied by Sieverts,1 who has shown that the gas is less soluble in. compact platinum than in the same weight of iron or nickel. At constant pressure the solubility rises with the temperature, whilst at constant temperature the amount of hydrogen absorbed is directly proportional to the square root of the pressure. On cooling, all the hydrogen absorbed at higher temperatures by the metal is evolved. 

The solubility of gases in alloys The study of gas-alloy systems has been confined principally to hydrogen. One might recognise two possible classes of alloy, one compounded of two hydrogen-dissolving metals, and the... 

Tomkins RPT (2003) Solubility of gases in mollrai salts and molten metals. Wiley Sct Solut... 

Apart from the possibility of gases being trapped inadvertently during casting, considerable difficulties can result from the marked differences in the solubility of gases in liquid and solid metals. An example of this is shown in Fig. 5.18. Examination of this figure indicates that... 

The T dependence of the solubility of CsH in Cs differs significantly from those for solutions of the hydrides in the other alkali metals. Distillation leaves behind involatile impurity salts, but oxygen transport from distilland to receiver has been observed. Oxygen can be carried over with the distillate in the form of COj or CO, the former being produced by decomposition of carbonate and the latter by reduction of oxides with a carbon impurity under dry conditions near the end of distillation. The identification of CO among the noncondensable gases during the distillation of Cs lends support to this. ... 

Gases can be (very) slightly soluble in molten metals. For example, the solubility, of nitrogen in liquid iron is well correlated by the empirical expression... 

---