40
Cyanide–3 (WAD)
7. Immediately push the D end of a Cyanide–3 collector tube over
the open end of each sample tube to start the seal.
8. Place the assembly in the press, putting the sample tube
through the hole in the white base. Before pressing the user
should grip the collector tube firmly at the breakaway point to
keep the tube from shifting during the pressing procedure.
9. The pressing motion should be a smooth constant pressure
which is just enough to slide the sample tube inside the
collector tube. A jerky, forced motion may cause added strain to
the tube and could potentially crack it. Press down on the
handle until the stop ring on the sample tube hits the
D end of
the collector tube.
10. Put on the heat-resistant gloves. Push the sample tube and
D
end of each tube all the way into the preheated block so that
the collector tube stop ring touches the block. Placing 21 tubes
should take less than one minute.
11. Set the timer for 30 minutes.
12. When 30 minutes is up, put on the heat-resistant gloves.
Remove the first tube from the block and immediately pull off its
sample tube using a downward, twisting motion as opposed to
a sideways motion. Remove the sample tube within 4 seconds
of removing it from the block or suck-back of the sample will
occur. Dispose of the sample tube and the hot solution left in it
by dropping it into the sink or waste bucket.
13. Invert each collector tube and place it into the collector tube
rack, with the
D end up. It should take less than two minutes to
pull and separate all 21 tubes.
14. Parafilm the
M end and allow tubes to cool for at least 10
minutes.
15. For each collector tube, hold the tube horizontally and rinse its
walls with the distillate in order to homogenize it. Slowly roll the
distillate around in the tube to gather all droplets clinging to the
tube walls into the bulk of the distillate. Then, slowly return the
collector tube to an upright position so that the
D end is up.
Stubborn drops will often fall into the
M end when the tube is
flicked with a finger.
16. With the
D end still up, break the collector tube in half by pulling
the
D end hard towards the user to break it, then twisting and
tearing off the
D end. Discard the D end.
17. In the remaining
M end of the collector tube, dilute to the 6.0 mL
mark with deionized water. This results in the original sample
volume, but now in 0.25 M NaOH.
18. Shake the tube with a gentle whipping motion to mix in diluent
water. Do not invert the sample. With the
M end down, place
the tube into the collector tube rack.
19. Determine the solution in the tube with Lachat's QuikChem
Method 10–204–00–1–X or equivalent. There is enough
distillate for two 25 second sample periods. Seal both ends of
the tube with Parafilm if the sample will not be determined
immediately.
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