PART III.

Earths atstd Earthy Salts,

621

supposed to be simple bodies, until the discoveries of Sir H.Davy revived the idea of their metallic nature.

The action of the pure earths on the animal economy is verysimilar to that of the alkalies.

The Earthy Salts * are compounds of the acids with thepure earths, resembling the salts formed by the combinationof acids with alkalies. Some of them are crystallizable, andsoluble in water; others are nearly insoluble : some of themexert scarcely any action on the animal economy; whileothers are possessed of great activity, and produce very strikingeffects.

In extemporaneous prescription, it is absolutely necessary toavoid combining the earths or earthy salts with substanceswith which they form insoluble compounds.

The following Table shows the solubility of the above earths,and of the compounds which they form with acids.

PureEarths.

Solubility inone part ofWater.

Acids which, in combination with theseEarths, form.

SolubleCompounds.

Compounds.Ucarcely soluble. \

InsolubleCompounds

ILinie.

Magnesia

Barytes.

Alumina.

0-002

0.000

0-050

0-000

Nitric

Muriatic

Acetic

Benzoic

Malic

Sulphuric

Phosphoric

Nitric

Muriatic

Carbonic

Acetic

Benzoic

Succinic

Malic

Nitric

Muriatic

Acetic

Benzoic

Tartaric

Sulphuric

Nitric

Muriatic

Carbonic

Acetic

Benzoic

Oxalic

Tartaric

SulphuricBoracicSuccinicTartaric

Tartaric

BoracicOxalic

SuccinicCarbonicCitric

Boracic

Oxalic

Phosphoric

Carbonic

Arsenic

SulphuricOxalicPhosphoricBoracic

Arsenic

PhosphoricArsenic

l We prefer the title garths and Earth;/ Salts to that of Earths and their Salts,