above this point, the formation of double salt is impossible. The retroflex portion of the curve represents solutions in equilibrium with carnallite and potassium chloride, but in which the ratio MgCl2 : KCl is greater than in the double salt.
Throughout its whole course, the curve EMK represents solutions in which the ratio of MgCl2 : KCl is greater than in the double salt. As this is a point of some importance, it will be well, perhaps, to make it clearer by giving one of the isothermal curves, e.g. the curve for 10°, which is represented diagrammatically in Fig. 114. E and F here represent solutions saturated for carnallite plus magnesium chloride hydrate, and for carnallite plus potassium chloride. As is evident, the point F lies above the line representing equimolecular proportions of the salts (OD).
Summary and Numerical Data.—We may now sum up the different systems which can be formed, and give the numerical data from which the model is constructed.[[366]]
I. Bivariant Systems.
| Solid phase. | Area of existence. |
| Ice | ABDC |
| KCl | CDEMKLNO |
| Carnallite | EFGHJKM |
| MgCl2,12H2O | BF1G1GFED |
| MgCl2,8H2O | G1H1HG |
| MgCl2,6H2O | H1I1IH |
| MgCl2,4H2O | I1L1LKI |
| MgCl2,2H2O | L1N1NL |
II. Univariant Systems.—The different univariant systems have already been described. The course of the curves will be sufficiently indicated if the temperature and composition of the solutions for the different invariant systems are given.
III.—Invariant Systems—Binary and Ternary.
| Point. | Solid Phases. | Temperature. | Composition of solution. Gram- molecules of salt per 1000 gram- mol. water. | |||
| A | Ice | 0° | — | |||
| B | Ice; MgCl2,12H2O | -33.6° | 49.2 MgCl2 | |||
| C | Ice; KCl | -11.1° | 59.4 KCl | |||
| D | Ice; MgCl2,12H2O; KCl | -34.3° | 43 MgCl2; 3 KCl | |||
| E |
| MgCl2,12H2O; KCl; carnallite |
| -21° | 66.1 MgCl2; 4.9 KCl | |
| F1 | MgCl2,12H2O | -16.4° | 83.33 MgCl2 | |||
| F | MgCl2,12H2O; carnallite | -16.6° |
| Almost same as F1; contains small amount of KCl | ||
| G1 |
| MgCl2,12H2O; MgCl2,8H2O |
| -16.8° | 87.5 MgCl2 | |
| G |
| MgCl2,12H2O; MgCl2,8H2O; carnallite |
| -16.9° |
| Almost same as G1, but contains small quantity of KCl |
| H1 |
| MgCl2,8H2O; MgCl2,6H2O |
| -3.4° | 99 MgCl2 | |
| H |
| MgCl2,8H2O; MgCl2,6H2O; carnallite |
| ca. -3.4° |
| Almost same as H1, but contains small amount of KCl |
| J1 |
| MgCl2,6H2O; MgCl2,4H2O |
| 116.67° | 161.8 MgCl2 | |
| J |
| MgCl2,6H2O; MgCl2,4H2O; carnallite |
| 115.7° | 162 MgCl2; 4 KCl | |
| K |
| MgCl2,4H2O; KCl; carnallite |
| 152.5° | 200 MgCl2; 24 KCl | |
| L1 |
| MgCl2,4H2O; MgCl2,2H2O |
| 181° | 238.1 MgCl2 | |
| L |
| MgCl2,4H2O; MgCl2,2H2O; KCl |
| 176° | 240 MgCl2; 41 KCl | |
| M | Carnallite; KCl | 167.5° | 166.7 MgCl2; 41.7 KCl | |||
| [N1 | MgCl2,2H2O | 186° | ca. 241 MgCl2] | |||
| N | MgCl2,2H2O; KCl | 186° | 240 MgCl2; 63 KCl | |||
| [O | KCl | 186° | 195.6 KCl] | |||
