( 1178 3 
95.641 2,519 0 1,840 0 CuSO,.5H;,0+D 
95,805 1.024 1,446 1,726 0 4 St 
94659 1406 2,313 0 1.622 s pe 
8 93.596 1,063 _ 3,804 0 1,537 ae 
5 91.744 0.909 7.817 0 1.500 . +, 
91.037 0,682 7.083 0 1.198 i ine 
n. 89.760 0587 8428 0 1,225  CuCl,.2H,0O+CuSO0,5H,0+D 
d. 97.546 2454 0 0 0 CuSO,.5H;O 
e. 90.534 0,42 9,042 0 0 CuCl,.2H,O0+4+CuSO,.5H,0 
96.405 0.687 0 2,509 0.399 D 
ie 95.574 0.664 0 9.960 1 0:802'\) 4, 
Z 94,689 0 1.831 0,852 2618 ‘ 
ri 93.078 0,603 9.589 0 2.730 
5. The wtsotherms between 25° and 15°. 
On decrease of temperature the isotherm at first retains a form as 
in fig. 2; the points 6 and c however approach each other, also the 
points p and #, and the points g and /. 
At 17,9° the points p and & coincide causing the saturation line 
pk of the anhydrous Na,SO, to disappear. The quadrangle (of course 
with curved sides) is then reduced to a triangle with the apexes q, / 
and the point at which p and & coincide. On further decrease of 
temperature this triangle gets smaller and disappears at 17.4° in a 
point. The solution represented by this point is saturated with four 
solid substances; if we also include the vapour there are six phases 
in equilibrium, so that we have a sextuple point. 
As four components are present in six phases, this system is non- 
variant. 
These phases are: 
Na,SO, + Na,SO, . 10H,O + NaCl + Na,Cu(SO,), . 2H,O 
+ solution + vapour 
Below 17°.4 the saturation surface of the Na,SO, therefore, dis- 
appears and the saturation surface of the Na,SO,.10H,O borders on 
that of the NaCl. 
On further decrease of temperature the points 6 and c rapidly 
move towards each other; at 16°.7 they coincide. Below this tem- 
perature the double salt Na,Cu(SO,), . 2H,O therefore disappears from 
the ternary system: water—Na,SO,—CuSO,. The double salt then 
