semi合集-English.pdf - 第4651页

SEMI C2.27-1102 © SEMI 1984, 2002 4 8.2.6.3 F E × 100 = % air Re p ort to the nearest 0.01% . 8.3 Sulfur Dioxide — This procedure de scribes the determi nation of sul fur dioxide in bor on trifluoride gas . A sample of t…

100%1 / 7923
SEMI C3.27-1102 © SEMI 1984, 2002 3
8.2.2 Apparatus
8.2.2.1 The modified gas collecting tube shown in
Section 8.1.1.7, Figure 2.
8.2.2.2 Separatory funnel, 2000-mL Pyrex (with 61-cm
Tygon
R
tubing and pinch clamp attached to stopcock
end).
8.2.2.3 Tygon tubing, 1/4 inch.
8.2.2.4 Balance, capable of weighing 1000 grams to
0.01 gram.
8.2.3 Reagents — All reagents used are reagent grade
unless otherwise indicated.
8.2.3.1 Water — All water used in the preparation of
reagents and in the procedure is either distilled or
deionized.
8.2.3.2 Sodium chloride solution — Dissolve 300 g of
sodium chloride in 1 liter of water.
8.2.4 Calibration - Gas Collecting Tube
8.2.4.1 Weigh the gas collecting tube to the nearest 0.1
g; weight = A, then clamp the tube securely on a
ringstand with the calibrated stem up.
8.2.4.2 Fill the tube with distilled water and allow it to
stand with the top stopcock open until it has reached
room temperature.
8.2.4.3 Record the room temperature to the nearest
0.01°C; temperature = °C.
8.2.4.4 Close the top stopcock. Drain and dry both of
the outer stems. Weigh the water-filled collecting tube
to the nearest 0.1 g; weight = B.
8.2.4.5 The net weight of the water in the tube (B - A)
in grams is equal to the volume of the tube in milliliters,
corrected for the density of water at temperature °C.
Determine this volume as follows:
V
olume in mL =
(B - A)
D - E
w
here D = Density (g/mL) of water
a
t temperature
°
C (from Table 1).
Table 1 Density vs T°C for Water
Temp. °C Density g/mL
20 0.99823
21 0.99802
22 780
23 756
24 732
25 0.99707
Temp. °C Density g/mL
26 681
27 654
28 626
29 597
30 567
8.2.5 Procedure
8.2.5.1 Obtain the sample of BF
3
gas in the gas
collecting tube. See Section 8.1.3 for sampling details.
8.2.5.2 Fill the separatory funnel with sodium chloride
solution. Attach Tygon tubing and a pinch clamp to the
funnel.
8.2.5.3 With a small dropper, fill the glass tubing
leading to the stopcock opposite the calibrated end of
the gas collecting tube with the salt solution. (Note: the
gas collecting tube is inverted at this point.)
8.2.5.4 Open the separatory funnel stopcock and the
pinch clamp on the Tygon tubing. Hold the tubing
upright and when it completely fills with NaCl solution,
slip the tubing onto the end of the gas collecting tube
which was previously filled in step 8.2.5.3.
NOTE 1: There should be no air bubbles in the connections
between the gas collecting tube and the separatory funnel. A
trace of a wetting agent such as Ultrawet (Atlantic Refining
Co.) in the salt solution assists in freeing small air bubbles
from the walls of connecting tubes.
8.2.5.5 Hold the gas collecting tube vertical, with the
calibrated end up and the entire collecting tube below
the liquid level of the separatory funnel.
8.2.5.6 Open the lower stopcock of the gas collecting
tube carefully and shake the tube to aid in dissolving of
the BF
3
gas in the salt solution.
8.2.5.7 Bring the liquid level in the gas collecting tube
equal to the liquid level in the separatory funnel.
8.2.5.8 Read and record the volume of undissolved gas
in the upper calibrated end of the gas collecting tube
and record this volume, to the nearest one-tenth of a
milliliter; mL = F. Record the room temperature.
8.2.6 Calculations
8.2.6.1 F = Total milliliters of undissolved gas (from
Section 8.2.5.8).
8.2.6.2 E = Total volume of gas collecting tube in mL;
see Calibration - Gas Collecting Tube.
SEMI C2.27-1102 © SEMI 1984, 2002 4
8.2.6.3
F
E
×100 = %air
Re
p
ort to the nearest 0.01%
.
8.3 Sulfur Dioxide — This procedure describes the
determination of sulfur dioxide in boron trifluoride gas.
A sample of the solution prepared in Section 8.1.4 is
titrated with standard iodine solution to a starch end-
point (blue). The sulfur dioxide is determined from the
equivalents of iodine used in the titration.
8.3.1 Method Capabilities: The range of this method is
5 ppm to 1500 ppm.
8.3.2 Apparatus
8.3.2.1 Burette, 10 mL, graduated in units of 0.05 mL.
8.3.2.2 Beaker, 250-mL.
8.3.3 Reagents — All reagents used are reagent grade
unless otherwise specified.
8.3.3.1 Water — All water used in the preparation of
reagents and in the procedure is either distilled or
deionized.
8.3.3.2 Iodine solution, 0.01 N — Prepare fresh daily
and standardize.
8.3.3.3 Starch indicator solution, 10 g/L — Prepare a
thin paste of 1 g of soluble starch with water. Pour the
paste with constant stirring, into 100 mL of boiling
water. Boil for one minute. Allow the solution to cool
and add 2.5 g of potassium iodide. Keep the solution in
a glass-stoppered bottle. Prepare fresh when the color
obtained for end points is violet or red instead of blue.
Alternatively, Thyodene dry indicator powder may be
used.
8.3.4 Operating Procedure
8.3.4.1 Calculate the amount of sample (prepared in
Section 8.1.4 that contains about 20 grams of BF
3
gas,
rounding off to the nearest milliliter. Calculate the
grams of BF
3
gas in this volume to the nearest 0.01 g,
using the “F” factor in Section 8.1.4.8. Transfer this
amount to a 250-mL beaker and add 5 drops of starch
indicator.
8.3.4.2 Using a 10-mL burette graduated in 0.05 mL,
titrate with iodine to a starch end-point (blue). Stir
constantly with a Teflon stir-bar or equivalent. Record
the volume of the iodine solution to the nearest 0.01
mL.
8.3.5 Calculations
mL I
2
×
Normality of I
2
×
0.032 × 1× 10
6
Grams of Water - Soluble Material
= ppm SO
2
where : 0.032 the milliequivalent weight of SO
2
;
1
×
10
6
is factor for conversion to
pp
m.
8.4 Silicon Tetrafluoride — This procedure describes
the determination of silicon tetrafluoride in boron
trifluoride gas. This method is based on the reaction of
soluble silica with molybdate ion to form a greenish-
yellow complex, B-silicomolybdic acid. This complex
is then reduced to a blue complex by 1-amino-2-
naphthol-4-sulfonic acid. The absorbance is measured at
650 nm and the amount of silicon tetrafluoride present
is obtained from a calibration curve.
8.4.1 Method Capabilities — The range of this method
is 45–450 ppm.
8.4.2 Apparatus
8.4.2.1 Photometer: One of the following is required,
with preference in the order given.
a. Spectrophotometer, suitable for measurements at
650 nm.
b. Filter photometer, for measurements from 640-700
nm, if less sensitivity is preferred.
c. Fisher Electrophotometer, with a red filter and 23-
mm cells.
NOTE 2: If the photometer being used measures in units other
than absorbance, the appropriate conversion to absorbance
must be made before calculating any results.
8.4.2.2 Absorption cells, 1.0-cm light path (for use with
a or b above).
8.4.2.3 Plastic beakers, 150-mL capacity.
8.4.2.4 Polyethylene weighing bottle with cap, 250-
mL.
8.4.2.5 Plastic volumetric flasks, 100-mL.
8.4.2.6 Plastic pipets, 0, 1.0, 2.0, 3.0, 4.0, 6.0, 8.0 and
10.0-mL sizes.
8.4.3 Reagents — All reagents are reagent grade unless
otherwise specified.
8.4.3.1 Water — All water used in this method is either
distilled or deionized and must be silica-free.
8.4.3.2 Boric acid solution, saturated — Dissolve 70 g
of boric acid, H
3
BO
3
, in 800 mL of hot water. Dilute to
1000 mL and mix. Store in a plastic bottle.
8.4.3.3 Ammonium molybdate solution, 10% —
Dissolve 50 g of ammonium molybdate,
SEMI C3.27-1102 © SEMI 1984, 2002 5
(NH
4
)
6
MO
7
O
24
4H
2
O, in water and dilute to 500 mL.
Store in a plastic bottle. Prepare fresh weekly.
8.4.3.4 Sulfuric acid, 5N, H
2
SO
4
— Carefully pour 35
mL of concentrated sulfuric acid into about 150 mL of
water in an ice bath. Cool to room temperature, dilute to
250 mL and mix. Store in a plastic bottle.
8.4.3.5 Tartaric acid solution, 40% — Dissolve 80 g of
tartaric acid in 140 mL of water. Dilute to 200 mL and
mix. Store in a plastic bottle. Prepare fresh weekly.
8.4.3.6 l-Amino-2-naphthol-4 sulfonic acid solution,
2.5 g/L — Dissolve 30 g of sodium bisulfite in 100 mL
of water in a 250-mL beaker. In a 100-mL beaker,
dissolve 1 g of sodium sulfite in 25 mL of water and
add 0.5 g of 1-amino-2-naphthol-4-sulfonic acid. Mix
the two solutions and dilute to 200 mL. Store in a
plastic bottle and filter before using. Prepare fresh
weekly.
8.4.3.7 Sodium silicate standard solution, 1 mL = 10
micrograms Si — Dissolve 1.012 g sodium silicate
(meta), Na
2
SiO
3
9H
2
O, in water in a 100-mL plastic
volumetric flask and dilute to volume. Pipet 10.00 mL
of this solution, using a polyethylene pipet, into a 1-liter
plastic volumetric flask and dilute to volume. One mL
of this dilution contains the equivalent of 10
micrograms Si.
8.4.4 Calibration
8.4.4.1 To a series of nine 150-mL plastic beakers,
pipet 0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, and 10.0 mL of
sodium silicate standard solution. These additions
correspond to 0, 10, 20, 30, 40, 50, 60, 80, and 100
micrograms of Si.
8.4.4.2 Into each beaker, pipet 25.0 mL of boric acid
solution. Dilute to about 60 mL with water and mix.
8.4.4.3 Continue with Procedure Sections 8.4.5.3–
8.4.5.9. Measure the absorption of each standard and
then return to Calibration, Section 8.4.4.4.
8.4.4.4 Subtract the absorbance of the 0 microgram
standard from each of the other standard absorbances
and plot the net absorbance versus the corresponding
micrograms of Si. Draw the best smooth line fitting the
points and passing through the origin.
8.4.5 Procedure (To be run in triplicate)
8.4.5.1 Calculate the amount of sample prepared in
Section 8.1.4 that contains about 0.5 g of BF
3
gas.
Transfer this amount to a polyethylene bottle and weigh
to the nearest 0.0001 g.
8.4.5.2 Wash this solution into a 150-mL plastic
beaker. Add 25 mL of boric acid solution. Dilute to
about 60 mL and mix.
8.4.5.3 Add 5 mL of ammonium molybdate solution
and mix.
8.4.5.4 Adjust the pH to 1.1-1.5 with 5N sulfuric acid.
Allow to stand 10 minutes.
8.4.5.5 Transfer the solution to a 100-mL plastic
volumetric flask and add 10 mL of tartaric acid
solution. Mix well.
8.4.5.6 Add 1 mL of 1-amino-2-naphthol-4-sulfonic
acid solution. Dilute to 100 mL and mix. Allow to stand
30 minutes.
8.4.5.7 Prepare a reagent blank by treating a 50-mL
aliquot of water as directed in Sections 8.4.5.2-8.4.5.6.
8.4.5.8 Set the wavelength of the spectrophotometer to
650 nm.
a. Single Beam Spectrophotometer — Rinse and then
fill a 1-cm absorption cell with water. Place the cell
into the cell holder and adjust the instrument to zero
absorbance.
b. Double Beam Spectrophotometer — Rinse and then
fill two matched 1-cm absorption cells with water
and zero the instrument with water in both beams.
Keep water in the reference beam and use the other
matched cell for the blank, standards and samples.
8.4.5.9 Rinse a second matched 1-cm absorption cell
with the blank solution and measure its absorbance.
Then, using the same cell, measure the absorbance of
each sample solution. Be sure to rinse the cell
completely with the solution to be measured before
each measurement. Recheck the instrument zero before
each measurement.
8.4.5.10 Subtract the blank absorbance from the
absorbance of the sample. Determine the corresponding
micrograms of Si from the standard curve.
8.4.6 Calculations
ppm SiF
4
=
Micrograms of Si× 3.706 × 1,000, 000
Weight of sample × 1, 000, 000
where :
3.706 converts Si to SiF
4
1,000, 000 converts ug to g
1,000, 000 converts to ppm.
8.5 Sulfate — This procedure describes the
determination of sulfate in boron trifluoride gas. Sulfate
ion is converted to a barium sulfate suspension under
controlled conditions in such a manner as to form
barium sulfate crystals of uniform size. Solutions are
added to stabilize the suspension and minimize
interferences. The resulting turbidity is determined by a
turbidimeter, filter photometer or spectrophotometer