Determination of SULPHATE from irrigation water sample.

Aim - Determination of Sulphate from irrigation water.

Principle

Sulphate iron are precipitate as Barium sulphate crystal of uniform size in acidic medium.

Method

Terbidimetric method.

Reagents 

1) Barium chloride ( Bacl2 . 2 H2O  crystal of  20-30)

2) conditioning reagent -

Dissolve 75 gram sodium chloride in 300 ml distilled water. Add 30 ml of concentrated HCL and hundred ml 95% ethyl alcohol (or isopropyl alcohol ) and 50 ml of glycerol and mix well and makeup volume to 500ml distilled water.

3) standard sulphate solution -

Dissolved 0.1479 gram of unhydrous sodium sulphate In distilled water and make up to 1000ml.

This gives 100 microgram per ml (PPM) solution of sulphate.

Procedure

1. Take hundred ml water sample into 250 Ml conical flask. 
2. Add 5 ml conditioning reagent and mix well using magnetic stirrer.                      The speed of stirring should be same for both sample and standard.
3.  While stirring add about 0.5 gram Barium Chloride crystal all at once and continued to stirr exactly to for 1 minute. 
4. Immediately after 1 minute pour for some solution into absorbance cell of spectrophotometer and measured the optical density at 30 second interval for 4 minute. Taking the maximum absorbance which will be normally after a period of 2 minute at 420 NM.
5.  Carry out a blank determination on Regent used. 
6. Pipette out 0, 10, 20, 30, 40, 50 ml standard sulphate solution of 100 microgram 1 ml separately in 250 ml conical flask. 

Add the balance distilled water. 100 ,90 ,80,70 ,60 ,50 ML to make hundred ml and repeat the procedure from Step 2 to step 4 for each flask and used the reading for floating standard curve from the standard curve, read sulfate concentration of given sample.  

Draw the graph factor. 

Calculations

Milli gram of sulphate /litre =

Mg Sulphate from standard curve × 1000 ÷ Ml of water sample.

Mg of sulphate / lit.  = Mg of sulphate Std. Curve × 1000/100

Mg sulphate /lit. = ----------

Rating for sulphate

<2	good quality watet.
2 to 12	medium quality water.
>12	bad quality water.

Results. 

In the given sample,  The sulphate content is -------mg/lit.