Cyanide
Cyanide
Cyanide_PP_Other_PPZ_Eng_Ody.fm Page 7 of 8
g. Using a water bottle, rinse the thistle tube with a small amount of
deionized water.
h. Allow the solution to mix for three minutes; then add 20 mL Magnesium
Chloride Reagent (Cat. No. 14762-53) through the thistle tube and rinse
again. Allow the solution to mix for 3 more minutes.
i. Verify that there is a constant flow of water through the condenser.
j. Turn the heat control to 10.
k. Carefully monitor the distillation flask at this point in the procedure.
Once the sample begins to boil, slowly lower the air flow to 0.3 SCFH. If
the contents of the distillation flask begin to back up through the thistle
tube, increase the air flow by adjusting the flow meter until the contents
do not back up through the thistle tube. Boil the sample for one hour.
l. After one hour, turn off the still, but maintain the air flow for
15 minutes more.
m. After 15 minutes, remove the rubber stopper on the 500-mL vacuum
flask to break the vacuum and turn off the water to the aspirator. Turn off
the water to the condenser.
n. Remove the gas bubbler/cylinder assembly from the distillation
apparatus. Separate the gas bubbler from the cylinder and pour the
contents of the cylinder into a 250-mL, Class A volumetric flask. Rinse
the gas bubbler, cylinder and J-tube connector with deionized water and
add the washings to the volumetric flask.
o. Fill the flask to the mark with deionized water and mix thoroughly.
Neutralize the contents of the flask and analyze for cyanide.
Calibration Standard Preparation
To perform a cyanide calibration using the Pyridine-Pyrazalone method, prepare
calibration standard containing 0.05, 0.100, and 0.200 mg/L cyanide as follows:
a. Prepare a 100-mg/L cyanide stock solution as described in the
Accuracy Check.
b. Into three different 1000-mL Class A volumetric flasks, pipet 0.50, 1.00,
and 2.00 mL of the 100-mg/L cyanide stock solution, respectively.
Use Class A pipets.
c. Dilute each flask to volume with deionized water. Stopper and invert
several times to mix.
d. Using the Pyridine-Pyrazalone method and the calibration procedure
described in the User-Entered Programs section of the Instrument Manual,
generate a calibration curve from the standards prepared above.
Accuracy Check
Standard Solutions Method
Caution: Cyanides and their solutions, and the hydrogen cyanide liberated by
acids, are very poisonous. Both the solutions and the gas can be absorbed
through the skin.
Prepare a 100 mg/L cyanide stock solution weekly as follows:
1. Dissolve 0.2503 grams or an equivalent amount of pure potassium cyanide in
deionized water and dilute to 1000 mL.
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