Kow we shall seek the position of the 6 bivariant regions, ti'rolil 

 curve (l)=i:2 + 3 + 4 tiie regions 23, 24 and 34 are starling. The 

 region 23 extends itself between the curves (1) and (4); it is indicated 

 in fig. 2 by 23. The region 24 is situated between the curves ^1) 

 and (3); the region 34 is situated between the curves (1) and (2) 

 and therefore, extends itself over curve (2) [tig. 2J. [We keep in 

 mind with this that each region-angle is smaller than 180°.] 



When we act in the same way with the regions which start from 

 the curves (2), (3) and (4) we find a partition of the regions as in 



fig- 2. 



Previously we have deduced : each region, which extends itself over 

 the stable or nietastable part of curve (i*],) contains the phase Fp. 

 We see the confirmation of this rule in fig. 2. The nietastable part of 

 curve (1) intersects the region 14, the stable part of this curve the 

 region 12; both the regions contain the phase 1. The metastable part 

 of curve (2) intersects the regions 12 and 24, which contain both 

 the phase 2 ; the metastable i)art of curve (3) intersects the regions 

 13 and 34 which contain both the phase 3. The metastable part of 

 curve (4) intersects the region 14, the stable part of this curve is 

 covered by the region 34 ; both the regions contain the phase 4. 



The following is apparent from the preceding considerations. In 

 all binary systems the partition and the position of the curves and 

 the regions will respect to one another starting from a quadruple- 

 point, is always the same; it can be represented by fig. 2. 



{To he continued). 



Chemistry. ^ "Compounds of the Arsenions Oxide." II. By Prof. 

 F. A. H. ScHREiNEMAKEKS and Miss W. C. de B.^at. 



a. Introduction. 



By Rüdorff') and others compounds are prepared of the As^O^ 

 with halogenides of potassium, sodium and ammonium. 



These compounds were obtained by treating solutions of arsenites 

 (viz. solutions of AsJ)^ in a base) with the corresponding halogenides. 



RüDORFF describes the compound As,0, . J^HfCl, which we have 

 found also; he also describes the compound {As^O,)^. KCl. which 

 we have not found. 



In order to obtain these compounds, we have, however, worked 

 in quite another manner; for this we have brought together water, 



1) Fr. Rüdokff. Ber. 19 26Ü8 (1886), 21 3051 



