399 



been borrowed from Reinders 's paper on : "Tlie Equilibria of Iron 

 and Iron Oxides with Watervapour and Hydrogen" '). 



The results of these calcnlations of the oxygen tensions have been 

 expressed in the following table 2. (See table 2 pag. 398). 



In (his table we find, therefore, (he oxygen-dissociation tensions 

 of the equilibria: 



2FeO :^ 2Fe + 0. 

 - 2Fe30, ^ 6FeO + (), 

 and 



Fe,0,^3FeH-20, 



and we- see from tliis that these expressions are very small, as was 

 to be expected. 



No importance is, of course, to be attached to the absolute values 

 of these pressiu-es, from which we should have to conclude to the 

 presence of one gas-molecule in many litres, when we continue to 

 consider the ordinai-y gas-laws as valid, because the formulae which 

 we used in our calculation rest on the supposition that we have 

 to do with a great number of molecules. Yet at the lower T the 

 real oxygen pressures corresponding to these calculated numerical 

 quantities will be so exceedingly small that the question suggests 

 itself whether (he oxidation of the reducing gas, which in (his case 

 proceeds wi(h pretty great velocity, can still be considered as a 

 homogeneous gas reaction.*) 



P,T- Projection of the Sf/slein — Fe. 



By the aid of these data we are now^ able to indicate part of (he 

 P,7'-projection of the system — Fe, when we put the found 

 oxygen-pressure equal to the total pressure. 



When in this projection we also indicate the points p and q 

 which would follow from Sosman and Hostettek's observations for 

 the vapour pressure of the equilibi'ium Fe203 -\- FcjO^ + G, corre- 

 sponding to (he (emperatures 1100° and J 200°, starting from the 

 supposition that the almost horizontal part of (he isodiermsof disso- 



I) i.e. 



~) Entirely analogous quesdons suggjesl themselves in the study of the mechanism 

 of the reactions between e.g. solutions and salts, or between metals with very 

 small solubility-product and electrolytes Especially in the latter case the numerical 

 values, which denote the electron concentration ui solution, can be exceedingly 

 small, as one of us showed already. *) 



*) Zeitschr. fur physik. Chemie 92, 1 (1916). 



26* 



