Group I. - Metals Of The Alkaline Earths. Calcium, Strontium, Barium,

Appendix. - Metals Of The Earths.

Aluminium, (? triad) Beryllium (dyad), Zirconium (tetrad), Niobium (tetrad), Cerium, Lanthanum, Didymium, Yttrium, Erbium (triads).

Group II. - Magnesium.

Group III. - Copper, Zinc, Silver, Cadmium.

Group IV. - Mercury.

This large class contains a number of metals which have widely different characters and reactions. Yet it will be seen from the following table that the successive addition of four reagents divides the metals tolerably nearly into those groups which agree in their physiological action. In some respects Groups I. and II. of Class 2 are perhaps more closely connected with the alkaline metals than with the heavy metals.

Reactions Of The Metals In Class II

Hydrochloric Acid

Sulphuretted Hydrogen

Ammonium Sulphide

Ammonium Carbonate

Ammonia and

Sodium

Phosphate

Group I.

Calcium..........

No precipitate.

No precipitate.

No precipitate.

White precipitate.

Strontium .......

Do.

Do.

Do.

Do.

Barium.............

Do.

Do.

Do.

Do.

(Appendix.)

Aluminium.......

Do.

Do.

White (Hydrate)

All other earthy metals............

Do.

Do.

Do.

Group II.

Magnesium. ..

Do.

Do.

No precipitate.

No precipitate.

White ppt. (phosphate).

Group III.

Zinc.................

Do.

Do.

White (sulphide)

Copper............

Do.

Black ppt.

Cadmium ....

Do.

Yellow ppt.

Silver..............

White curdy ppt. soluble in ammonia.

Black ppt.

Group IV.

Mercury as subsalt..................

White ppt.

Black ppt.

Do.as persalt..

No precipitate

Do.

It must be borne in mind that the above reagents are used successively, and each remains in the solution. Thus when ammonium sulphide is added, part of it is decomposed by the hydrochloric acid and ammonium chloride is formed. It is on account of the presence of the ammonium chloride in the liquid that magnesium is not precipitated by the ammonium sulphide, while aluminium is.