Two methods of сyanide analysis

1. TWO METHODS OF СYANIDE
ANALYSIS
Kairatkhan Lazifa
Al-Farabi Kazakh National University
Almaty, Kazakhstan

2. Cyanide, colorimetric, pyridine-pyrazolone

3. APPLICATION
1.1 The method may be used to determine cyanide
in water and water-suspended sediment
containing at least 0.01 mg/L of cyanide.
1.2 This method may be used to determine cyanide
in bottom material containing at least 0.5 mg/kg.
1.3 Total cyanide in water-suspended sediment may
be determined if each sample is shaken vigorously
and a suitable aliquot of well mixed sample
withdrawn.

4. SUMMARY OF METHOD
This method is based on the chlorination of cyanide
and the subsequent reaction of the product with a mixed
solution of pyridine-pyrazolone to form a stable complex
dye. The method detects only simple cyanides;
therefore, any complex cyanides present must be broken
down. The decomposition of complex cyanides is
accomplished by an acid reflux and distillation prior to
the colorimetric procedure. The distillation also removes
certain interferences from water samples.

5. INTERFERENCES
3.1 Common interferences include sulfide, heavy-metal
ions, fatty acids, steam-distillable organic compounds,
cyanate, thiocyanate, glycine, urea, oxidizing agents, and
substances that may contribute color or turbidity to the
sample.
3.2 These interferences may be removed or their effect
minimized as follows:
3.2.1 Sulfide can be removed as lead sulfide by adding a
slight excess of lead carbonate to 400 mL of the alkaline
(pH 11.0 or above) sample. Filter the sample immediately,
wash the precipitate with demineralized water, and add the
washings to the filtrate.

6. 3.2.2 Fatty acids can be removed by acidifying 400 mL of
sample with acetic acid to a pH of between 6 and 7, and
by extracting with 80 mL of either isooctane or hexane. A
single extraction is usually sufficient.
3.2.3 Oxidizing agents can be removed by adding sodium
sulfite solution to 400 mL of sample until a negative test
with starch-iodide paper is obtained.
3.2.4 Most remaining interferences are removed by the
distillation.
3.3 This method includes no provisions for removing these
interferences or for minimizing their effects in watersuspended sediment and bottom material. The analyst
must be aware that, when such interfering substances
are present, the analytical result obtained may be in
error, although distillation of the cyanide certainly
separates it from some of the interfering substances.

7. APPARATUS
4.1 Distillation train (fig. 1). An efficient gas washer is
essential to the proper operation of the distillation
assembly. The Fisher-Milligan unit has been found
satisfactory.
4.2 Heating element for Claisen flask.
4.3 Spectrometer for use at 620 nm.
4.4 Refer to the manufacturer's manual to optimize
instrument.

8. Figure 1. -Cyanide, distillation train

9. Greenness Profile information developed in cooperation with the Green
Chemistry Institute
Method Number
PBT
I-3300
Green
Corrosive
Green
Hazardous
Green
Waste Amt
Not Green
Assumptions/Comments
N.S. -- not specifiedN.A. -- not applicable

10. Cyanides, Amenable To Chlorination
(Titrimetric; Spectrophotometric)

11. SCOPE AND APPLICATION
1.1 This method is applicable to the determination of
cyanides amenable to chlorination in drinking, surface
and saline waters, domestic and industrial wastes.
1.2 The titration procedure is used for measuring
concentrations of cyanide exceeding 1 mg/L after
removal of the cyanides amenable to chlorination. Below
this level the colormetric determination is used.

12. SUMMARY OF METHOD
A portion of the sample is chlorinated at a pH > 11
to decompose the cyanide. Cyanide levels in the
chlorinated sample are then determined by the method
for Cyanide, Total, in this manual. Cyanides amenable to
chlorination are then calculated by difference.

13. REAGENTS
3.1 Calcium Hypochlorite solution: Dissolve 5 g of calcium hypochlorite
(Ca(OCl)2) in 100 mL of distilled water.
3.2 Sodium Hydroxide solution: Dissolve 50 g of sodium hydroxide
(NaOH) in distilled water and dilute to 1 liter.
3.3 Ascorbic acid: crystals.
3.4 Potassium Iodide-starch test paper.

14. 4.0 PROCEDURE
4.1 Two sample aliquots are required to determine cyanides
amenable to chlorination. To one 500 mL aliquot or a
volume diluted to 500 ml, add calcium hypochlorite
solution (3.1) dropwise while agitating and maintaining
the pH between 11 and 12 with sodium hydroxide (3.2).
4.2 Test for residual chlorine with KI-starch paper (3.4) and
maintain this excess for one hour, continuing agitation.
4.3 After one hour, add 0.5 g portions of ascorbic acid (3.3)
until KI-starch paper shows no residual chlorine. Add an
additional 0.5 g of ascorbic acid to insure the presence of
excess reducing agent.
4.4 Test for total cyanide in both the chlorinated and
unchlorinated aliquots as in the method Cyanide, Total, in
this manual.

15. 5.0 CALCULATION
5.1 Calculate the cyanide amendable to chlorination
as follows:
where:
A = mg/L total cyanide in unchlorinated aliquot
B = mg/L total in chlorinated aliquot

16. Greenness Profile information developed in cooperation with the Green
Chemistry Institute
Method Number
PBT
Corrosive
Hazardous
Waste Amt
335.1
Green
Green
Green
Not Green
Assumptions/Comments
residual chlorine test is considered
N.S. -- not specified N.A. -- not applicable

17. Thank
you for attention!