Yesterday I did my first cyanide titration. 
This was based on GoldSilverPro's 2009 post cyanide titration, which was significantly clearer than the 11 pages given me from a professional mining services company. I first put together my own notes (shown below) and did a couple of qualitative tests to familiarize myself with what to expect at the end point. Without an indicator, the cloudy white was very difficult to detect, so I was glad that the end point with rodanine was very clear. (I didn't have any KI.)
Analysis for free Cyanide:
(1) Pipette a 10 ml (K or Na) cyanide sample into a 250 ml erlenmeyer flask. [sample A]
(2) Add 90 ml of distilled water. [sample A/10]
(3) Add: [indicator]
- Nothing, if no indicator is to be used, or
- 5 ml of 10% KI (potassium iodide) solution, or
- 5 ml rodanine.
(4) Titrate with standard 0.1 N AgNO3 (silver nitrate) solution until: [standard B]
- a faint white turbidity persists (no indicator)
- a faint yellowish turbidity persists (KI indicator)
- the canary yellow colour changes to salmon pink (rodanine indicator)
The standard AgNO3 solution is prepared by weighing out exactly 17.00 grams [0.1M=0.1N AgNO3]
of the reagent grade salt and dissolving it in distilled water, [AgNO3 = 169.88 gm]
after which it is diluted to exactly 1 liter in a volumetric flask.
(5) The Sodium Cyanide (NaCN) in gm/liter is equal to: [NaCN gm/L in A = 0.9825 x B ml]
0.9825 x ml of 0.1 N AgNO3 used. [1M NaCN = 49.01 gm 2N = 98.02]
(If KCN (potassium cyanide) is being used, [(KCN gm/L in A = 1.306 x B ml)]
the KCN in gm/liter = 1.306 x ml of AgNO3 used.) [1M KCN = 65.03 gm 2N = 130.06]
(Being the sceptic that I am) I cross-checked all the figures and found some differences based on my calculations of molar wts. My figures in blue and GSP's figures from his source in red. Have I made a mistake or is there a good reason for the differences?
This was based on GoldSilverPro's 2009 post cyanide titration, which was significantly clearer than the 11 pages given me from a professional mining services company. I first put together my own notes (shown below) and did a couple of qualitative tests to familiarize myself with what to expect at the end point. Without an indicator, the cloudy white was very difficult to detect, so I was glad that the end point with rodanine was very clear. (I didn't have any KI.)Analysis for free Cyanide:
(1) Pipette a 10 ml (K or Na) cyanide sample into a 250 ml erlenmeyer flask. [sample A]
(2) Add 90 ml of distilled water. [sample A/10]
(3) Add: [indicator]
- Nothing, if no indicator is to be used, or
- 5 ml of 10% KI (potassium iodide) solution, or
- 5 ml rodanine.
(4) Titrate with standard 0.1 N AgNO3 (silver nitrate) solution until: [standard B]
- a faint white turbidity persists (no indicator)
- a faint yellowish turbidity persists (KI indicator)
- the canary yellow colour changes to salmon pink (rodanine indicator)
The standard AgNO3 solution is prepared by weighing out exactly 17.00 grams [0.1M=0.1N AgNO3]
of the reagent grade salt and dissolving it in distilled water, [AgNO3 = 169.88 gm]
after which it is diluted to exactly 1 liter in a volumetric flask.
(5) The Sodium Cyanide (NaCN) in gm/liter is equal to: [NaCN gm/L in A = 0.9825 x B ml]
0.9825 x ml of 0.1 N AgNO3 used. [1M NaCN = 49.01 gm 2N = 98.02]
(If KCN (potassium cyanide) is being used, [(KCN gm/L in A = 1.306 x B ml)]
the KCN in gm/liter = 1.306 x ml of AgNO3 used.) [1M KCN = 65.03 gm 2N = 130.06]
(Being the sceptic that I am) I cross-checked all the figures and found some differences based on my calculations of molar wts. My figures in blue and GSP's figures from his source in red. Have I made a mistake or is there a good reason for the differences?
