FIELD OF THE INVENTION:
This invention relates to a method for estimation of Fluoride content in caster
compounds.
BACKGROUND OF THE INVENTION:
The Intertek laboratory in Antwerp, Belgium provides fluorine and fluoride testing.
The lab uses a Antek 9000F Fluoride analyzer. The fluoride, fluorine testing
instrument uses pyro-hydrolysis with ion specific electrode (ISE) detection, and
runs testing according to the UOP975-02 method.
The current method involves the analysis of fluoride by Spectrophotometric in
mainly water. As caster compounds are heterogeneous mixture of inorganic
constituents. Main advantages of this process are i) ease solution making ii) High
accuracy with high repeatability and iii) free from other elemental interference.
OBJECTS OF THE INVENTION:
An object of this invention is to propose a method for estimation of fluoride
content in caster compound;
Another, object of this invention is to propose an efficient method for the analysis
of fluoride in caster compound;
Still another object of this invention is to propose an accurate method for the
analysis of fluoride in caster compounds.

DETAILED DESCRIPTION OF THE INVENTION:
According to this invention there is provided a method for estimation of fluoride
content in caster compounds comprising:
Preparing solution of zirconyl chloride, sodium 2(-parasulfophenylazo)-, 8-
dihydroxy-3,6-naphthalene disulfonate] and sodium arsenite solution,
mixing the solution of zirconyl chloride and sodium zirconyl acid and (SPADNS)
in 1:1 ratio;
preparing standard sodium fluoride sodium;
subjecting the standard sodium fluoride solution and unknown solution to the
step of calibration after adding the mixture of zirconyl-SPADNS and sodium
accurate solution;
measuring the absorbance of the solutions by spectrophotometer.
A quantitative analytical method for fluoride content flux material was developed.
This casting flux consists of mainly silica and magnesium base materials.
Accurate determination of Fluoride ion in these materials will provide the vital
information to fluidity of the material in refractory technology.
The new procedure for determination of fluoride was developed and various
factors that could affect the tests were verified. Pure fluoride compound and
certified material standard were tested using this method. Testing result had
excellent agreement with actual certified value.
Zirconyl-chloride solution: Weigh 0.08 gm Zirconyl chloride octahydrate
(ZrOCI2,8H2O) and transfer to a 250 CC volumetric flask. Add around 50 CC of
fluoride free distilled water and 175 CC of concentrated Hydrochloric acid and
make up the volume with distilled water addition.

SPADNS solution [Sodium 2(-parasulfophenylazo)-1, 8-dihydroxy-3, 6
naphthalene disulfonate]: Weigh 0.25 gms of SPADNS and transfer to a 250 CC
volumetric flask and dissolve it using distilled water. Protect it from direct sunlight
for maintaining stability for longer periods.
Mixture of Zirconyl chloride and SPADNS solution: Mix Zirconyl acid and
SPADNS in 1:1 ratio. The mixed solution is stable for longer periods.
Sodium arsenite solution: Weigh 0.25 gm of sodium arsenite (AR grade) and
transfer to a 250 CC volumetric flask and dissolve it in distilled water.
Standard Fluoride Solution:
Stock solution: Dissolve 0.5526 gm of 100% pure anhydrous sodium fluoride in
distilled water and dilute to 250 ml which is equivalent to 1000ppm of fluoride
solution. In case of 99% purity, take 0.5582 gm of NaF and dissolve in water and
dilute to 250 ml.
Calibration solution: Take 10 ml of 1000 ppm stock solution and dilute to 100 ml
to obtain 100 ppm stock solution. Take 5 ml of 100 ppm stock and dilute to 100
ml to obtain 5 ppm working solution.
Operation of Spectrophotometer
I. Fixed wave length mode of operation: If the wave length of color
compound to be monitored is known, directly go to linear or quadratic
option. Enter the fixed wave length, no of standards to be used for
calibration, no of samples to be tested and click the user base line and
OK it. Enter the concentration of each standard one by one and follow

the instructions displayed. After completion, the spectrophotometer
displays a message for reference solution. Then introduce the reference
solution i.e., blank solution in both cells (reference and measurement
cells). After reference measurement is over, the spectrophotometer
displays messages for standard samples sequentially. Introduce standard
-1 solution in the measurement Cell and the reference cell should contain
the blank solution only. Continue to follow the instructions. After
completing the measurement with all the standards, spectrophotometer
displays the calibration curve. Store the same.
II. Scanning mode of operation: If the wave length of the colour
compound to be monitored is not known, click on search wave length
and follow the instructions displayed on the screen. Introduce the test
solution in the measuring cell. After searching the wave length, use this
wave length and follow the method as described in the above step.
Calibration and measurement by Spectrophotometer:
A. Calibration
Take 0.5582 gm of 99% pure Sodium Fluoride and dissolve in fluoride free
distilled water and dilute to 250ml which is equivalent to 1000ppm. (Say: solution
no:1).
Take 10 ml of solution no:1 in a 100 ml volumetric flask and makeup the volume
to 100ml. to obtain 100 ppm concentration (say solution:2)
Take 5 ml of solution no: 2 in a 100 ml volumetric flask and makeup the volume
to 100ml. to obtain 5 ppm concentration (say solution:3)
Take 1ml, 2ml, 4ml, 8ml and 16 ml of solution mentioned in step 3 above, in five
different 100 ml flasks.

Take another 100ml flask and mark it as Blank.
Add 5 ml of Zirconyl-SPADNS solution to each flask, followed by 1 ml of Sodium
arsenite solution. Makeup the volume by adding fluoride free water up to the
mark. Measure the absorbance of the solutions in linear/quadratic mode at 570
nm wavelength, by adjusting the absorbance of the blank solution as a reference.
The measurement should by completed within 30 mts of the final stage of
preparation i.e., addition of Zirconyl-SPADNS mixture, otherwise results will not
be representative.
As soon as the measurement is completed, calibration graph is displayed. Store
it.
Introduce the unknown solutions.
Calibration solutions:


Preparation of test sample solution:
Take 0.1 gm sample in a platinum crucible, mix with 2 gm of sodium carbonate
and 1 gm of borax, fuse the mass over burner or muffle. Dissolve the molten
mass in 250ml beaker by adding 10% hydrochloric acid. After completion of
dissolution, cool and transfer to a 250 ml volumetric flask. This is treated as a
mother solution. This solution is further diluted in such a proportion that
concentration of the solution should fall in between 0.2 ppm to 0.8 ppm.
Reporting the result:
Multiply the concentration displayed on the spectrophotometer with the dilution
factor and report the result.
% Fluoride=
{(volume) X (subsequent dilution factor) X (reading in ppm of the
spectrophotometer) X 0.0001} / (wt. of the sample)

WE CLAIM:
1. A method for estimation of fluoride content in caster compounds comprising:
preparing solution of zirconyl chloride, sodium 2(-parasulfophenylazo)-, 8-
dihydroxy-3,6-naphthalene disulfonate] and sodium arsenite solution,
mixing the solution of zirconyl chloride and sodium zirconyl acid and (SPADNS)
in 1:1 ratio;
preparing standard sodium fluoride sodium;
subjecting the standard sodium fluoride solution and unknown solution to the
step of calibration after adding the mixture of zirconyl-SPADNS and sodium
accurate solution;
measuring the absorbance of the solutions by spectrophotometer.

2. The method as claimed in claim 1, wherein Zirconyl chloride solution is
preferred by adding 0.08 gm Zirconyl chloride octahydrate distilled water and
concentrated hydrochloric acid.
3. The method as claimed in claim 1, wherein sodium 2(-parasulfophenylazo)-
1,8-dihydroxy-3, 6 naphthalene disulfonate] is preferred by adding 0.25 gms of
SPADNS and distilled water.
4. The method as claimed in claim 1, wherein sodium arsenite solution is
preferred by adding 0.25 gm of sodium arsenite and distilled water.
5. The method as claimed in claim 1, wherein standard fluoride solution is
preferred by dissolving 0.5526 gm of pure anhydrous sodium fluoride in
distilled water and dilute to 250 ml.

6. The method as claimed in claim 1, wherein the % of fluoride is calculated as
follows:
% Fluoride=
{(Volume) X (subsequent dilution factor) X (reading in ppm of the
spectrophotometer) X 0.0001} / (wt. of the sample)

A method for estimation of fluoride content in caster compounds comprising:
preparing solution of zirconyl chloride, sodium 2(-parasulfophenylazo)-, 8-
dihydroxy-3,6-naphthalene disulfonate] and sodium arsenite solution, mixing the
solution of zirconyl chloride and sodium zirconyl acid and (SPADNS) in 1:1 ratio;
preparing standard sodium fluoride sodium; subjecting the standard sodium
fluoride solution and unknown solution to the step of calibration after adding the
mixture of zirconyl-SPADNS and sodium accurate solution; measuring the
absorbance of the solutions by spectrophotometer.