7oa 



of the infra-red bauds for tliree gases ^). Tliis agi'eement appears 

 from the foregoing table, in which the values of the three first 

 mentioned gases are derived from Mandersloot. 



I hope soon to come back to the application of the used expres- 

 sions to some other equilibria. 



Postscript. During the correction of the proofs a treatise by 

 0. Stern in the Annalen der Physik of June came under my notice, 

 in which an expression is derived which shows close resemblance 

 with that of Prof, van der Waals. Application on the iodine 

 equilibrium can also here lead to a small moment of inertia, which 

 is however considered improbable by Stern. 



Amsterdam, Sept. 1914. Anorg. Chem. Laboratory 



of the University. 



Chemistry. — ''Equilibria in the .njstem Pb — >S' — 0; the roasting 

 reaction process'. By Prof. W. Reinders. (Communicated 

 by Prof. S. Hoogewerff). 



(Communicated in the meeting of Sept. 26, 1914). 

 Introduction. 



1. The manufacture of galena into metallic lead is mostly carried 

 out in this manner that the sulphide is first partially roasted and 

 the mass then again strongly heated with unchanged or freshly 

 added lead sulphide out of contact with air. Lead is then formed 

 with evolution of SO^. 



The reactions that take place in this process known under the 

 name of "Rostreactionsarbeit" are generally given in the text-boolis 

 as follows: 



PbS -f 20, = PbSO, 

 2 PbS + 30, = 2 PbO + 2 SO, 

 and then : PbS + PbSO, = 2Pb + 2 SO, 

 PbS + 2 PbO --= 3 Pb 4- SO, 



1) Mandersloot. Thesis for the Doctorate. Utrecht. 1914. 



