{2}. Green mass.

Having now given the principal reactions for the most important metals,
we will proceed to the examination of the alkali metals, the alkaline
earths, and some of the acid elements.

THE ALKALI METALS

17. ~Ammonium, NH_{4}.~--This hypothetical compound is commonly classed
among the alkali metals from its close resemblance to the members of
this group.

To detect the presence of this hypothetical metal, mix the assay with
about four parts of Na_{2}CO_{3}, place in an ignition tube, and apply
heat. The odor of the evolved gas will be recognized, and if a piece of
red litmus paper be moistened and held at the mouth of the tube, it will
be turned blue by the escaping ammonia gas.

We are not authorized to infer the pre-existence of ammonium, however,
from the appearance of this reaction, for the presence of nitrogenous
organic matter in the substance, which would be decomposed by this
treatment, would give rise to such a reaction.

18. ~Potassium.~--Potassium is recognized by the color which its salts
impart to the Bunsen flame. If a portion of a salt of potassium be held
on a platinum wire in the flame, it imparts a blue-violet tint which
rapidly disappears.

19. ~Sodium.~--Like potassium, this alkali metal is detected by the color
which its salts give to the flame.

If a sodium salt be held on the platinum wire in the flame, it imparts
an intense yellow color.

The extreme delicacy of this reaction has been mentioned elsewhere. The
value of this test is really lessened by its great delicacy, for it is
possible to detect minute quantities of sodium in almost all substances,
although it may not be in chemical combination. As an example, draw the
platinum wire between the fingers, and then place in flame, and note
presence of sodium.

20. ~Lithium, Li_{2}O.~--In the Bunsen flame on the platinum wire it
imparts a carmine-red tinge.

Hydrochloric acid on the sample augments the coloration.

THE ALKALINE EARTHS

21. ~Barium, BaO.~--In the Bunsen flame on the platinum wire it imparts an
apple-green coloration. This reaction is intensified by moistening the
sample with hydrochloric acid.

22. ~Calcium, CaO.~--In the Bunsen flame on the platinum wire it imparts
an orange-red color, which appears gray when seen through blue glass.

Hydrochloric acid on the sample makes the color more intense.

23. ~Strontium, SrO.~--In the Bunsen flame on the platinum wire it imparts
an intensely