ASTM E359-10 Analysis of Soda Ash (Sodium Carbonate)

Scope:

The standard test methods for analyses of soda ash are covered by ASTM E359-10 standard method. The following analytical procedures appear under mentioned sections:

Procedures	Sections
Total Alkalinity, Titrimetric	8-15
Sodium Bicarbonate, Titrimetric	16-23
Loss of Heating, Gravimetric	24-30
Moisture, Calculation	31-35
Sodium Chloride, Titrimetric	36-42
Sodium Sulfate, Gravimetric	43-49
Iron, Photometric	50-58
Sieve Analysis	59-65

Test procedure:

Total Alkalinity- Titration with standard hydrochloric (or sulfuric) acid using methyl orange or modified methyl orange indicator solution.

Sodium Bicarbonate- The bicarbonate is converted to carbonate by adding sample to excess standard sodium hydroxide solution. Barium chloride solutions are used to precipitate the carbonate. Standard acid solution back-titrates the excess sodium hydroxide using pH meter to determine the end point.

Loss of Heating- Loss on heating is determined gravimetrically by heating a weighed sample under controlled conditions to expel moisture and thermally convert sodium bicarbonate to sodium carbonate by elimination of water and carbon dioxide.

Moisture- it is determined by calculation.

Sodium Chloride- A sample is dissolved, acidified, and treated with a small excess of standard silver nitrate solution. The precipitated silver chloride is removed by filtration and the excess silver nitrate is titrated with standard ammonium thiocyanate

solution using ferric ammonium sulfate indicator solution. This is the Volhard method.

Sodium Sulfate- Sulfate is determined gravimetrically by precipitation with barium chloride solution, filtering, washing, igniting, and weighing as barium sulfate.

Iron- Iron is determined photometrically as the orange-red complex of the ferrous form with 1,10-phenanthroline in an acetate-buffered solution at pH 5. The colour develops within 15 min. Intensity of the colour formed is measured at 510 nm in a photometer calibrated with standard iron solutions.

Sieve Analysis- The material is passed through a series of sieves arranged in order of increasing fineness and calculating the cumulative percentage of each screen fraction.

Specimen size: The size of the sample shall be sufficient to perform all analyses without the reuse of any portion of the sample.

Data:

The percent loss in weight is calculated as follows,

A = mass of bottle and sample before heating, B = mass of bottle and sample after heating, and W = sample used

Percent moisture is given as,

A = loss on heating %, and B = sodium bicarbonate %