12. Could barium hydroxide be used in place of calcium hydroxide in testing for carbon dioxide?
CHAPTER XXV
THE MAGNESIUM FAMILY
| SYMBOL | ATOMIC WEIGHT | DENSITY | MELTING POINT | BOILING POINT | OXIDE | |
| Magnesium | Mg | 24.36 | 1.75 | 750° | 920° | MgO |
| Zinc | Zn | 65.4 | 7.00 | 420° | 950° | ZnO |
| Cadmium | Cd | 112.4 | 8.67 | 320° | 778° | CdO |
The family. In the magnesium family are included the four elements: magnesium, zinc, cadmium, and mercury. Between the first three of these metals there is a close family resemblance, such as has been traced between the members of the two preceding families. Mercury in some respects is more similar to copper and will be studied in connection with that metal.
1. Properties. When heated to a high temperature in the air each of these metals combines with oxygen to form an oxide of the general formula MO, in which M represents the metal. Magnesium decomposes boiling water slowly, while zinc and cadmium have but little action on it.
2. Compounds. The members of this group are divalent in nearly all their compounds, so that the formulas of their salts resemble those of the alkaline-earth metals. Like the alkaline-earth metals, their carbonates and phosphates are insoluble in water. Their sulphates, however, are readily soluble. Unlike both the alkali and alkaline-earth metals, their hydroxides are nearly insoluble in water. Most of their compounds dissociate in such a way as to give a simple, colorless, metallic ion.