1226 
I’ is the same (namely, /’”= vapour F”) AW and A V are also the same 
for both systems. The curves a'D and a’K’ must, therefore meet 
in the P, T-diagram in the point /. 
A corresponding property holds when a corresponding point / is 
situated on the four-phase curve, or on the melting point curve of 
the complex #—-+ fF". 
Hence, if the sublimation line, the four-phase line or the melting 
point line of the complex / + /” is in a part a congruent and in 
a part a transition curve, the curve of the complex in the P, 7-dia- 
gram will meet in its transition point the corresponding curve of 
that compound which is being converted. 
If there are two transition points, many cases may present them- 
selves, according to their situation, the compound converted ete., 
which we will not discuss here any further. 
(To be continued). 
Chemistry. — “The system sodium sulphate, manganous sulphate 
and water at 35°'). By Prof. F. A. H. ScHREINEMAKERS and 
D. J. vaN Proowe. 
In this system occur as solid phases, which can be in equilibrium 
at 35° with saturated solutions: anhydrous Na,SO,, the hydrate 
MnsSO,.H,O and the two anhydrous double salts : 
Doo == (Mn SO) : (Na, SO4)10 and Dis == Mn SO. (Naz SO4)3. 
The double salts previously described: 
Mn SO,. Na, SO, , 2H20 and Mn SO,. Naz 50, . 4 H.O 
have not been found by us, whereas on the other hand those now 
noticed have not been described up to the present. Moreover, the 
accurate preparation and solubility of the salts previously described 
are but insufficiently known, so that it is difficult to decide whether 
these are perhaps metastable or whether the presence of two meta- 
stable salts was, perhaps, due to accident. 
The equilibria occurring at 35° are indicated schematically in the 
figure; the two double salts are represented by the points Doo and 
D,3, the salt MnSO, . H,O is represented by the point Mn,. The isotherm 
consists of four branches, namely 
1) Marienac and Geiger, A. Min. [5] 9. 15. Mag. Pharm. 11 27, 
