| The interfering effects due to various ceramic constituents
such as aluminium, titanium, zirconium and alkalies on the
radiation signal of calcium have been critically studied in
both hydrochloric and sulphuric acid media using a Oamephotometer
with light filter and low flame temperature such
as town gas, air or LPG air-flame. It has been observed that
in hydrochloric acid medium AI, Ti and Zr have quenching
effect on the radiation signal of calcium even at low concentrations
while in sulphuric acid medium it has hardly
any effect when AI: Ca and Ti: Ca ratios are less than 1/S
and Zr: Ca ratio is less than one. It has also been observed
that the radiation signal of calcium is almost completely
quenched when the AI: Ca, Ti: Ca and Zr: Ca ratios are
~ S, ~ 4 (~ 8 in HCI) and ~ 20 respectively in HCI and
H,so. media due to the formation of CaO, AI20 3 ; CaO,
Ti02 and CaO, Zr02 spinels. Magnesium in concentration
of 200 or more times of calcium can quantitatively release
calcium from AI, Ti and Zr in the range present in alumino
silicates only in H,SO, medium due to the preferential
formation of MgO, AI20 3 spinel. Based on these observations,
a simple flame-photometric method has been worked
out in which calcium radiation signal is first completely
quenched and subsequently released by the addition of
adequate amount of magnesium. The method is accurate,
sensitive and utilized for determination of smaU amount of
calcium in various ceramic materials. |
