[hannibal]

please suggest me a method for quantitative analysis of alkaline hydrazine(2%-3%) in solution with hypochlorite and urea (solution obtained during the synthesis of hydrazine)..i have seen somewhere that iodine solution can be used but coulnot find much on that

[hannibal]

i need a method that uses simple chemicals available at lab....i dont have access to things like GC

[kevins]

A spectrophotometric method for ppb level Hydrazine:
The hydrazine react with p-dimethylaminobenzadehyde to give a yellow complex. Determine the concentration at 455nm.

A Iodine titration method for ppm level Hydrazine:
Add ~0.2gm of sodium bicarbonate solid to the sample. Titrate the sample with standard Iodine solution.

[hannibal]

A Iodine titration method for ppm level Hydrazine:
Add ~0.2gm of sodium bicarbonate solid to the sample. Titrate the sample with standard Iodine solution.

are you sure kevins that this method works well in the presence of sodium hypochlorite and for 2-3%hydrazine....and would you please tell me the role of sodium bicarbonate in this titration,i already have sodium hydroxide in the solution.

[asqa]

Hydrazine
References: ASTM D 1385-88 (Reapproved 1991), Hydrazine in Water.
L. C. Thomas and G. J. Chamberlin, Colorimetric Chemical Analytical Methods, 8th ed., p. 195, method I (1974).
Hydrazine, N2H4, is a powerful reducing agent which is used in various chemical processes as a raw material, and in boiler water as an oxygen scavenger.

To control corrosion, residual hydrazine typically is maintained in the range of 0.05 to 0.1 mg/L. Higher levels may be used. to guard against corrosion when the boiler is out of service for an extended period.

The Colorimetric Method. CHEMetrics' method is based on PDMAB, paradimethylaminobenzaldehyde. PDMAB in acid solution reacts with hydrazine to form a yellow product. Results are expressed as (mg/L) N2H4.

hope this is enough.Please suppress the hypochlorite by adding acid then proceed the above analysis

[asqa]

for further help go to the link

http://www.chemetrics.com/analytes/hydrazine.html

[kevins]

hannibal,

The hydrazine titration method is from JIS B8224 section 18.2:(sometime the JIS method is hard to read and I copy from their english translated copy) Iodine Titrimetric Method for Hydrazine determination: Range : 0.4 mg or more.
1. Reagents
a. Sodium Bicarbonate.
b. N/20 Iodine solution: Dissolve 20gm KI in water. dissolve 6.35gm Iodine and make up to 1-L.

2. Operation.
a. Take a suitable quantity of sample into a 300-mL Erlenmeyer flask, and add water to 100 mL.
b.Add 2 gm sodium bicarbonate ( I make a mistake 0.2gm in my previous post) to make the solution weak alkali.
c. Add 1mL starch indicator solution.
d. Titrate with N/20 Iodine solution and take the time when the blue colour of iodine is confirmed (in about 30 sec) as the end point.
e. Carry out the blank test with 100mL water.
f. Calculate the concentration of hydrazine in sample:
N = (a-b)x f x 0.4 x 1000/V
Where N= hydrazine (mg/L)
a: N/20 iodine solution required for titration (mL)
b: N/20 iodine solution required for blank ittration (mL)
f: factor of N/20 iodine solution
V: volume of sample used
0.4: hydrazine equivalent quantity of N/20 iodine solution 1 mL(mg)

Please note that the "method" havn't say this can be applied to the sample contains sodium hypochlorite. We apply this method to the clear water sample with ppm level of hydrazine.
Please try by yourselves the "interference".

[hannibal]

thanks a lot kevi for this detailed method.can you also tell me the oxidation reduction reaction involved

[kevins]

Iodine is an oxidizing agent

Hydrazine is a reducing agent.

Do you know how to write the reaction?

[hannibal]

NH2NH2 + 2I2 + 2Na2CO3 --------> N2 + 2NaI + 2H2O + 2CO2
i guess that is the reaction taking place.....pls confirm it

[kevins]

As per my previous post, what is the function of NaHCO3?

[hannibal]

i messed betw sodium bicarbonate and sodium carbonate,i think this is the correct one....
NH2NH2 + 2I2  + 4NaHCO3 -----> N2 + 4NaI + 4H2O + 4CO2

[kevins]

No,

The function of sodium bicarbonate is provide the weak alkali medium.

The main reaction is hydrazine and Iodine.

[arnyk]

That's what I was thinking, usually NaHCO3 is used to increase pH.

[hannibal]

thats exactly what i have done the main reaction is indeed between I2 and NH2NH2, the product of this reac. should give HI which will react with NaHCO3 to give NaI.