Determination of Concentration of Sulphate

Determination of Concentration of Sulphate
  • Author: Farhan Khan
  • Posted On: July 5, 2020
  • Updated On: July 5, 2020


The water has various chemical components mixed naturally in it to fill up the nutritional components by nature. These have a specific proportion or quantity to be in the water to be authentic and nutritional in use. These consequents when get exceeded from the standard values they tend to make the sample poisonous and not feasible for use. The major aspect is now how to determine these exceeding or the decreased content. This quantity for the Sulphur is determined through the following methods for determination explained as under.

Related theory:

A SO4 has a high distribution in nature with its presence in the H2O in variable proportion in the limits of thousands to mg/liter. The quantity of Sulphur content is highly under consideration because of its contribution in the factors leading towards the management and dealing of water problems.

These issues such as odor rise in parallel to the corrosion of the sewer pipes takes place due to the excess quantity of the sulfate content. This results in the creation of the hydrogen sulphide due to atmospheric anaerobic conditions.

The determination of the SO4 content can be evaluated by the following approaches:

  1. ignited residue gravimetric technique
  2. dried residue gravimetric technique
  3. scheme of turbidimetric

Ignited residue gravimetric technique:

SO4 ions reside in HCl. This process is passed out under a significantly high temperature corresponding to the steaming point after which the left-out sample is solidified, passed through water, and ignited. This is assessed later.

Dried residue gravimetric technique:

The content is an organic dominating material than the method adopted at priority is drying up of the precipitates rather than ignition.

The method of turbidimetric:

This ,method has its basics on the principle that barium sulphate has more tendency for precipitation in the form of colloids which gains an increment of an additional amount of NaCl having with organic compounds & glycerol. This absorption capacity of BaSO4 is evaluated through a turbidimeter or nephelometer whose comparison is made with the values obtained through standards.

Equipment / chemicals:

The apparatus involved are

  • The drying oven + desiccator
  • A steam-bath
  • An analytical weighing balance
  • A filter paper (whatman)
  • A furnace of muffle
  • A glass funnel
  • Pipette
  • A measuring flask
  • Methyl indicator
  • HCl solution
  • Silver nitrate & BaCl solution

apparatus for the turbidimetric-method are as follows:

  • Turbidimeter or nephelometer
  • A stirrer (magnetic)
  • A stopwatch
  • A ml spoon for measuring
  • A conditioning agent
  • A solution of BaCl
  • A standard solution of SO4


The procedure for the precipitate-ignition method is as follows:

  1. A 250 ml of testing sample is measured in a container.
  2. The adjustment of acidity is passed out by using HCl at a pH of 5 through pH measuring instrument.
  3. An additional amount of HCl is added up in the mixture 1-2 ml.
  4. The mixture is now boiled up to the heating temperature.
  5. The residue of mixture is weighed before placing it to boil the sample.
  6. The precipitation of the mixture when placed the mixture is cleaned out of the filter paper.
  7. This filtered residue is now bathed and again heated up by putting it muffle surface at a temperature of 800.
  8. the mixture is then cooled down by using the desiccator.
  9. The weight is now defined of BaSO4.

Residue-drying method:

The procedure adopted for residue drying is all same except last steps. i.e. residue is dried up in the atmospheric air rather than heating up.

Turbidimetric method:

  1. A specific proportion of given mixture is taken in a separate container.
  2. A reagent of 5 ml is added followed by the mixing of the mix.
  3. One spoon of BaCl crystals is combined with stopwatch turned off simultaneously.
  4. The mixture is continuously mixed at a uniform speed for 1 minute.
  5. The mixture is than poured into the preoccupation cells for the turbidity measurement observed after every interval of 30 sec.
  6. A curve for the calibration is now plotted.
  7. A graph is plotted against the absorbance with the intensity of SO4.
  8. The transmission density is determined for the given mixture which helps in the quantity of the SO4 in the mixture.


Sr. # Sample vol ml Crucible empty wt + F.P Wt of residue + F.P Wt. of BaSO4 Mg/L of SO4
1. ——– ——– ——– ——– ——–
2. ——– ——– ——– ——– ——–
3. ——– ——– ——– ——– ——–
4. ——– ——– ——– ——– ——–


Wt. of F.P = ——– (mg)

SO4 ions (mg/L) = mg of BaSO4/ ml of mixture * 411.6 = ——

Sr. # mg/L of SO4
1. ——–
2. ——–
3. ——–
4. ——–


The proportion of the mixture are determined and later compared with standard values and comments are centered on them.


Following are the precautionary ways are adopted:

  1. Measuring flask should be properly calibrated.
  2. Instruments must be rinsed thoroughly.
  3. Heating should be taken place in accordance with the model set.
  4. Evaluating the weight should be conducted with proper care.
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Author: Farhan Khan

Farhan is a highly experienced civil engineer from the Southern side of Texas and has been associated with ConstructionHow since 2020. Over almost a decade, his wide span of expertise enabled him to bring forth his fair share of stories and experiences related to the most iconic engineering examples worldwide. He has also contributed to online and offline publications on requests. Engineering is his passion, which is why he chose to become part of our honorable team of industry experts looking to provide authentic and credible guidelines to the reader.