1113 
line WD», intersects this curve 6d in the point c, the salt NH,AsO, 
is soluble in water at 30° without decomposition. The saturated 
aqueous solution of this salt is represented by point e; it is apparent 
from the position of the points JV, ¢ and Mo, with respect to one 
another that this solution contains = 19.2 "/, NH,AsO,. 
We have deduced with the aid of the rest-method the composition 
of the solid phase, which is in equilibrium with the solutions of 
branch bed. The conjugationlines liquid-rest are going viz. all through 
the point Dyii. As the point Do 31, however, is situated close to 
Dai, the conjugationlines for the solutions of branch be go within 
the errors of analysis, also through the point Ds3;. Although 
it is, therefore, sure that the solutions of cd which are situated at 
some distance of c, are saturated with Di, = NH,AsO,, yet the 
possibility exists that the other solutions are saturated with Do 3) = 
NH,H,AsO,. 
It is apparent from the table that branch bcd is determined no 
further than to a solution d, which contains 14,28°/, NH,. In order 
to examine if with higher content of NH, in the solution perhaps 
still a compound should occur with more NH, than in the compound 
NH,AsO,, we have still examined a solution at 0°, which contained 
36,05°/, NH,. It was apparent that also in this case the solid phase 
was still the NH,AsQ,. 
From the course of curve ab and from table 1 it is apparent 
that the solubility of the As,O, increases strongly with increasing 
content of ammonia of the solution. The terminating point 5, viz. the 
solution which is saturated with As,O, + NH,AsO,, is not determined. 
The solution of branch ab which is experimentally determined and 
which is situated the nearest to the point 6 contains (compare table) 
21.17°/, As,O, and 2,86°/, NH,. It is apparent from the course of 
the branches a/ and dcd that the solution 4 will contain + 22°/, AsO, 
and + 2,87°/,NH,. From this it appears, therefore, that small 
quantities of NH, strongly increase the solubility of the As,O,. 
We imagine in tig. 1 the line NH,—¢ to be drawn; its point of 
intersection with the side JV—As,O, is represented in the figure 
by /; this point f indicates a complex which contains + 22,5 °/, 
As,O, and consequently + 77,5 °/, water. Now we take a complex 
e, situated between a and /; this contains, therefore, more than 
2,26 °/ and less than 22,5°/, As,O, and consequently it consists 
of solution « + solid As,O,. When we bring NH,-gas into this 
complex, then it follows the line e—NH, ; this line intersects, starting 
from e, firstly the region ab As,O,, afterwards the region Wabed 
and further the region bed D211. Hence it follows that by adding 
