Environmental Express MicroBloc - Manual (Page 14)

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HotBlock: Operation and Instruction Manual MicroBlock TM Distillations
Total Cyanide Distillation with the MICROBLOCK TM Continued
6.8 Potassium Cyanide, Working Standard
Prepare a series of standards covering the working range. Dilute 10mL of the Intermediate Standard to 100µL with
reagent water. Concentration of 1mL = 10µg CN. Prepare fresh daily or before each use.
7.0 PROCEDURE
7.1 Pipette 50mL of sample or an aliquot diluted to 50mL with reagent water into the MicroBlock Reaction Flask.
Add a pinch of boiling chips. For solid samples weigh 1g or less to the nearest 0.01g, dilute to 50mL and
add boiling chips.
7.2 Pipette 50mL of 0.25N NaOH into the Absorption Flask. If using the Snip & Pour concentrate pour the entire 10mL of
the 1.25N NaOH into the absorption flask. Dilute to 50mL using DI Water. Refer to the schematic for the appropriate
placement positions and flexible tubing connections to cool the Cold Finger with running tap water. All air/vacuum
valves are in the OFF position.
7.3 Repeat 7.1 and 7.2 for all samples to be distilled up to a maximum of 10.
7.4 Position the Cold Finger and Absorber Impingers.
7.5 Turn tap water ON after assuring all tubing connections are firmly placed. A water flow rate of 50 to 60 gallons per
hour is required.
7.6 Turn ON the vacuum and slowly adjust each valve to provide an air flow bubble rate of several bubbles per second
for each position as viewed in the absorption vessel.
7.7 If nitrate-nitrite is known to be present add 5mL of sulfamic acid reagent through the reagent inlet. Allow the air
flow to mix for several minutes.
7.8 Slowly add 5.0mL of 18N sulfuric acid though the reagent inlet.
7.9 If iron cyanide complexes are known to be present add 2.0mL of magnesium chloride reagent. If excess foaming
occurs, add an additional 2mL. Allow a few minutes to mix.
7.10 Turn the heat ON and set the temperature of the heating block to 150°C.
7.11 Set the timer for 1 hour.
7.12 Timer will automatically turn OFF power to the heater block at the pre-selected time.
7.13 Disconnect the Distillation Head and Absorption Impinger by separating the Slip Connector. Turn air/vacuum valves
to the OFF position. Repeat for each sample position.
7.14 Allow the tap water to continue circulating through the Cold Fingers which will cool the heater block more rapidly in
preparation for the next run.
7.15 The distilled cyanide in the 0.25N NaOH solution is now ready for analysis.
7.16 Immediately after the run is finished, place the Absorption Impinger in distilled water. Do not let the impinger dry
out since the NaOH may clog the frit.
7.17 If the frit becomes clogged, clean with concentrated HCl using an ultrasonic bath. If this procedure is not successful
use aqua regia.
7.18 After use clean exterior surfaces with a damp sponge. For acid spills sponge with a diluted solution of sodium
carbonate followed by distilled water.