Cobalt solution check
Photometric linearity check
If the photometric linearity of the instrument is
questionable, first check your analytical procedure and
technique (see Techniques on page 2-2). Ifproper
operation is still in doubt, use the Photometric
Accuracy/linearity Test from SPECTRONIC8'
Standards (Cat. No. 333150) to test and evaluate
photometric performance of your instrument.
To prepare a stock cobalt solution:
I. In a I-liter volumetric flask, place 200 mL distilled
water. Slowly and cautiously add 10 mL
concentrated hydrochloric acid (ACS grade). Mix
and make to volume with distilled water to obtain
I % hydrochloric acid solution.
2. In a I-liter volumetric flask, place 22 to 23 gm
cobalt chloride (CoC~, ACS grade). Dissolve in the
I % hydrochloric acid. Make to volume with 1%
hydrochloric acid to obtain cobalt chloride stock
solution.
The alternate method below uses specially prepared
potassium dichromate solutions.
To perform the cobalt solution check:
I. Turn on the Power Switch/Zero Control and allow
the instrument to warm up for at least 15 minutes.
2. If you have a SPECTRONIC" 20D or 20D+, set the
display mode to Transmittance.
3. With the sample compartment empty and the cover
closed, adjust the Power Switch/Zero Control until
the meter or display reads O%T.
4. Set the Wavelength Control to 500 nm.
5. Set the Filter Lever to 340 -599nm.
6. Insert the glassware filled with distilled water into
the sample compartment and use the
Transmittance! Absorbance Control to set the meter
or display to lOO%T.
7. Replace the distilled water with the cobalt chloride
solution.
8. Insert the glassware filled with the cobalt chloride
solution into the sample compartment.
9. Read %T on the meter or display.
10. Repeat steps 4 through 9 at 505,510,515 and
520 nm. The instrument is in proper calibration
when minimum transmittance (maximum
absorbance) occurs between 505 and 515 nm. The
specific transmittance (or absorbance) values are
unimportant.
Wavelength calibration adjustment
If the wavelength accuracy is out of tolerance, refer to
the Service Procedure section on page 3-5. Customer
recalibration is not recommended.
I. Turn on the Power Switch/Zero Control and allow
the instrument to warm up for at least 15 minutes.
2. Make sure that the sample compartment is empty
and the cover is closed, then adjust the Power
Switch/Zero Control until the display reads O%T.
3. If you have a SPECTRONICII200 or 200+, set the
display mode to Absorbance.
4. Prepare O.OIN sulfuric acid diluent by adding 0.3mL
of concentrated sulfuric acid to about 500mL of
deionized or distilled water in a clean I L volumetric
flask. Fill to volume with deionized or distilled
water.
5. Prepare a stock solution of potassium dichromate by
weighing 0.500g of potassium dichromate (e.g.,
Fisher Certified A.C.S. potassium dichromate,
formula weight 294.19) and dissolving it in about
400mL ofO.OIN sulfuric acid solution in a 500mL
volumetric flask. Fill to volume with O.OIN sulfuric
acid solution. This is your stock 1.0g/L potassium
dichromate solution.
6. Measure 2.5mL of the stock 1.0g/L potassium
dichromate solution into a clean lOOmL volumetric
flask containing about 75mL O.OIN sulfuric acid
solution. Fill to volume with O.OIN sulfuric acid
solution. This is your 0.025g/L potassium
dichromate solution.
7. Measure 5.0mL of the stock 1.0g/L potassium
dichromate solution into a clean lOOmL volumetric
flask containing about 75mL O.OIN sulfuric acid
solution. Fill to volume with O.OIN sulfuric acid
solution. This is your 0.05g/L potassium dichromate
solution.
8. Set the Wavelength Control to 350nm.
9. Set Filter Lever to 340 -950nm.
To Next Page
Loading...
Need help?
General
