. 120 



weiglied acciii-atel^y ; this complex imist tlieii be siliialed on a straight 

 line with the solution and tlie rest formed from this. This was 

 always the case in this examination. 



When in tig. 1 we draw the conjngalionlines, which nnite the 

 solntions of l)rauch he with the corresponding rests, those donotgo, 

 as is drawn in tig. 1. through liic same point D. When we call 

 the percentages of A.^^J), antl water of a solution Yi and !(',, those 

 of the corresponding rest Y, and IF,., and when we call Yf tlie 

 percentage of As.^0, of the point D (the point of intersection of the 

 line liqnid-rest with the side As^JJ^ — IF) then we find: 



y,— Yi 

 Yf = Yr A X W,: 



When we calculate with the aid of this formula }7 for the deter- 

 minations 4 — 11 of table 1, we find 



76.29; 76.35; 75.52; 75.45; 75.04; 77.86; 75.65; 76.30. 



As the compound A.i.,<>^. K('l contains 72.6% AsJJ^ and the com- 

 pound {AsJJ^)^ KCl contains 84.1 7» As J),, the point D, therefore 

 cannot represent this compound, it is more probably (J.v,^),)^ (/vt'/)^. 

 which contains 76.1"/,, AxJJ^ or {A.'i.,Ot)i,[KCt), which contains 

 76.97u As^O^. When we taUe the average of the eight determina- 

 tions, then we find IQ.QS" j^ As.,(J,, which is in accordance with the 

 composition of (As,(\),^ [KCl)^. 



When we draw in tig. 1 the line WD, we see that this does not 

 intersect the saturationcurve of I), but that of the AsJ}^. Conse- 

 quently the compound is not soluble in water without decomposition, 

 but is decomposed with separation of As^O^. 



c. The system: HJ)—As,Ü,-NH,Cl at 30^ 



In this system both tiie components ^4»'.j03 and A'^Z/^CY and further 

 a compound D occur at 'MY. We found for the composition of 

 this componnd, which is determined with the aid of the rest-method, 

 As,0,.NH,Cl 



We may represent the isotherm of 30° in this system again 

 schematically by fig. 1; the anglepoint Z represents then the A'//., (7/ 

 and the point D the compound AsJ)^ . NH^CI. Consequently the 

 isotherm consists again of three branches, viz. : 



ah, tlie saturationcurve of As,()^ 



be, „ „ „ Afi,C\. NH,Cl= D 



c'l, „ „ „ NH.Cl. 



9 

 Proceedings Royal Acad. Amsterdam. Vol. XVIll. 



