Page 230 - Chemistry ICSE Class IX

4 Flame Test

BASIC CONCEPTS
2+
2+
2+
The ame test is based upon the fact that salts (particularly chlorides) of certain metals like Cu , Ba , Sr ,
+
+
2+
Ca , Na , K , etc. on heating in an QZKFKUKPI ƀCOG volatilise and KORCTV characteristic colours to the ame.
From the colour of the ame, it is quite easy to detect the presence /absence of certain metal ions in any
sample.
Procedure
Follow the steps given below to conduct the ame test on a compound:

y Make a loop of platinum wire by winding it around the tip of a pencil, as shown below in Fig 4.1(a):

Fig. 4.1
y Make a thick paste of the given salt with 2-3 drops of conc. HCl on a watch glass [Fig 4.1(b)].
y Take a small amount of this paste on the cleaned platinum wire loop.

y Heat it in the oxidising flame [Fig 4.1(c)].
y Note the colour imparted to the flame with naked eyes as well as through blue cobalt glass.
y Compare the flame colour with the metal/metal ion as given in the table given below.

TABLE 4.1 Flame tests for various salts
%QNQWT QH VJG ƀCOG 1ZKFKUKPI Inference
With naked eye Through blue glass Metal ion present Metal present
Golden yellow Invisible Na + Sodium
Violet (purple) Pink K + Potassium
Brick-red Olive green Ca 2+ Calcium