what is purity?

what is purity?

What is purity? A measure of the net content of a substance.
The materials used in the lab or industry have some impurity.
They usually have different impurities.
Use purity or purity to indicate the net content of the material
Which follows the following relationship:
Mass of gross mass / Mass of pure matter = Degree of purity
Mass of gross mass / 100 * Mass of pure matter = Percent purity
For example, when we talk about sodium chloride 90% it means
If we divide this piece of salt into 100 parts, it is 90 parts pure sodium chloride and 10 parts are impurities.


Chemical formula: Na-OH

Molecular Weight: 40 CAS: 1310-73-2

RTECS: WB490000

Synonyms: Sodium hydroxide, caustic soda

Features: It is an odorless, white crystalline, transparent, non-volatile and highly corrosive.

Moisture absorbs air easily.


OSHA: 2 mg / m3

NIOSH: 2 mg / m3 / 15 min C; Group I Pesticide

ACGIH: 2 mg / m3 C

Materials and solutions required:

Sodium carbonate, with the original standard purity

Solution Acetate hydrochloric acid, 0.1 normal;

The basic standard is Sodium carbonate.

Hydrochloric acid, 0.01 normal; 10 ml of the acetic acid solution of hydrochloric acid 0.1 normal

Place in a 100 ml bottle of distilled water.

Distilled water is deionized, free of CO2, boiled then cooled with nitrogen.

Compressed Nitrogen

sodium hydroxide 50% (w / v);
50 g of caustic soda dissolved in distilled water

And the volume of 100 ml.

make a caustic soda stokes, 0.1 normal;
add 8 ml of 50% caustic soda to 1 liter CO2-free distilled water.

the practical standard solution of caustic soda, 0.01 normal;
10 ml solution of caustic soda stoke

Exert a 0.1% normal boil with 100 ml CO2-free distilled water

The standard buffer solution with pH 4 and 710-

Required equipment:

Sampler: 37 mm PTFE membrane filter with 1-micron pore size
(Millipore, Fluorophore or similar types).

With a celluloid support pad, with cassette in the filter holder.

Individual sampling pump with a discharge rate of 4-1 L / min,
with flexible interface pipes

pH meter with pH electrode and recorder

Titration container; balloons of 150 to 200 ml;

With a cover that has a hole for the PH electrode as well as the input and output N2

Magnetic stirrer

Glass rod, 5 mm in diameter and 10 cm in length,

To keep the filter below the liquid level in the titration vessel

Pipettes 5 and 10 ml

Balloons of 100 ml and 1 liter

A 50 ml burette with a grade of 0.1 ml



Calibrate individual sampler pumps.

Also, attach a sampler to the pump during calibration.

Perform sampling in a flow rate between 4-1 L / min for air volume flow of 70 to 1000 liters.

Do not allow more than 2 mg of total dust to be collected on the filter.


Transfer the sample filter to the titration container by tweezers.

Note that the surface on the filter is downward.

Due to the fact that during the analysis of the filter below the liquid level,

Place the glass rod end on the filter center to hold it.

Cover the titration container.

Add 5ml hydrochloric acid 0.01 in a titration vessel.

The titration vessel was placed in a magnetic stirrer and purified by N2 (0.1 L / min)


Let the titration container stay in the mixer for 15 minutes.

Calibration and quality control

Calibrate the pH gauge using buffer solutions (with pH equal to 4 and 7).

Adjust the amounts of 0.1% hydrochloric acid solution to sodium carbonate.

3 to 5 grams of standard sodium carbonate for 4 hours at 250 ˚C.

Then cool it in the desiccator.

Dissolve 2.5 g of sodium carbonate in 1 liter of CO2-free distilled water

And to obtain a sodium carbonate of 0.05 normal.

Transfer 5 ml of sodium carbonate solution 0.05 to the titration container

Start titration and continue until you reach PH 5.

Remove the PH electrodes and rinse it into the titration container.

To remove the dissolved CO2, add N2 to the contents of the titration container for 3 to 5 minutes.

Continue titration to the turning point.

Calculate the acidity of the hydrochloric acid solution by the following equation:

N_HCl = ((weighing g Na_2 CO_3) (titration in the case of use NaCl CO 2) / ((52.99)) used HCl ()

The practical Standard solution of caustic soda with the normal solution with the homogeneous hydrochloric acid solution.

Perform this according to step 2 of calibration, except that the hydrochloric acid solution is homogeneous

Alternate with sodium carbonate solution (Na2CO3) and a 0.1% normalized caustic soda solution with the normal hydrochloric acid solution.

Calculate the normality of the caustic soda titration using the following equation.

N1aOH = ((N-HCl) (mL HCl used)) / (mL NaOH used)

Prepare at least three spike checks in order to check the amount of recycling in the range for which the sample is intended.


The excess hydrochloric acid in the main sample, control and spike samples

Reverse titration with standardized (coherent) caustic soda.

Simultaneously clean up with nitrogen.

Look at the PH meter as you type.

Determine the end point (ml of caustic soda used normal 0.01)


Carbon dioxide in the air may

Reacts on the filter with alkali and forms carbonates

But it does not interfere with the titration.

Carbonates can cause positive interference.

Acid particles can neutralize the sample and have negative interactions


Calculate the concentration of caustic soda in the air using the following equation:

C = ((V_ (NaOH-b) -V_ (NaOH-S)) .N × 40 × 〖10〗 ^ 3) / V

In this regard:

C = concentration of caustic soda in mg / m3

The NaOH-b = volume of caustic soda in the titration of the control sample in milliliters

The NaOH-s = volume of caustic soda in the titration of the original sample in milliliters

N = Sodium nitride solution normalization

40 = Molecular weight of caustic soda

V = Sample volume of air in liters

The Caustic soda of Arax production group with a purity of 98.5% is ready to supply domestic and foreign markets.

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Industrial production of caustic soda
Industrial production of caustic soda

 Industrial production of caustic soda

 Industrial production of caustic soda

 Sodium Hydroxide is a solid and white substance with a melting point of 1388 ° C and

a density of 13.2.

This material usually reaches 98% or 99% purity for various uses Sodium hydroxide is

presented in four ways in terms of its appearance:

Caustic soda liquid

Sodium hydroxide liquid is Produced by Using the Hydrolysis Process of a Salt Solution,

in Petrochemicals and Liquid caustic soda production Units then will be transported by

special thanks to caustic soda flakes production units.

Caustic soda flakes

Caustic soda flakes are usually in white color and odorless material and are available at the flake.

Caustic soda pearls:

Caustic soda pearls are solid, white and similar to small snowball bullets,

which are used in more precision and finer production?

It is commonly used in pharmaceutical and textile industries with more sensitive applications

Sodium Hydroxide Powder:

This caustic soda or sodium hydroxide, have fairly small grains.

The process of sodium hydroxide production

More than 95% of the chlorine production capacity and approximately 100% of sodium hydroxide

production capacity is based on the hydrolysis of brine Dissolution.

In this process, the sodium chloride solution is decomposed electro less to chlorine

(gas chlorine) and sodium hydroxide and hydrogen.

If instead of using salt water (sodium chloride),

a calcium chloride solution or potassium chloride as the raw material is used,

The reaction product will contain potassium or calcium instead of sodium.

There are also processes where hydrogen converts liquid chloride into hydrogen

and chlorine,

or sodium melted chloride to chlorine and metallic sodium.

In producing liquid sodium hydroxide, using sodium chloride as the raw material,

about 1126 kg of sodium hydroxide and 28 kg of hydrogen are produced per 1000 kg of chlorine.

A large amount of hydrogen produced in this process is used to produce ammonia,

hydrochloric acid, and hydrogenation of organic compounds.

  Sodium hydroxide production method

Three methods for producing caustic soda:




Producing liquid sodium hydroxide with diaphragm method:

Using the diaphragm method, chlorine, sodium hydroxide (Noah),

and hydrogen is produced simultaneously.

In this process, the two reactor sections are separated by a

permeable diaphragm plate, often made of asbestos.

In the diaphragm reactor, saturated brine enters the anode portion of the cell,

where the chlorine gas is released, and then It flows to the Cathode section.

The role of the diaphragm in this method is to isolate the salt solution from

the liquid sodium hydroxide in the cathode,

where the hydrogen gas is released there.

The product of the process is a dilute solution of Brine and liquid sodium hydroxide.

In this solution, the liquid Density should reach 50% and the salt should be removed.

Sodium hydroxide is spilled over into nickel trays for Condensation.

And is heated at 1400 ° C to condensation from 50% to 98%.

So, about 3 tons of water evaporates per ton of liquid sodium hydroxide

 Produce liquid sodium hydroxide with membrane method:

The most common method of sodium hydroxide production is hydrolysis of salt water

in a membrane cell.The difference in this method with the diaphragm method is that

around each of the electrodes in the solution,

surrounded by a diaphragm surrounded by a membrane.

The saturated salt water enters the first reactor chamber
(where chlorine gas is released)It turns out.

Chloride ions are oxidized by the anode and converted to chlorine gas

by losing electrons. In the cathode, the positive ions of hydrogen,

which are obtained by the decomposition of water molecules,

The electric current is restored to the hydrogen gas and the hydroxide

ions released into the solution are released.The ion penetrating membrane in

the middle of the cell only allows for positive ions of sodium to cross into the second part of the cell

While chloride ions remain in the anode section.

In the cathode, hydroxide ions react with sodium ions to produce sodium hydroxide.

The Obtained sodium hydroxide has a significantly lower sodium chloride (salt)

As a result, it has a higher purity and higher quality than diaphragm production

And there is no need for a desalination process.

Produce liquid sodium hydroxide with mercury method:

In this method known as the Kestner-Kellner Process, the salt water saturation

the solution is placed above a thin layer of mercury.

In this process, mercury plays a role as a cathode and interacts with the sodium

formed in the solution, and a mixture of sodium and mercury (amalgam) is obtained.

Sodium-mercury amalgam is continuously released from the reactor and reacted with water,

which leads to the decomposition of this mixture with sodium hydroxide, hydrogen, and mercury.

The mercury is recovered from the mercury process and the chlorine formed in the anode is released

into the gas from the reactor.

Production of caustic soda flakes

Caustic soda is produced by utilizing the liquid caustic soda of petrochemicals during the process

of thickening and evaporation.

The process of producing caustic soda flakes is such that at first sodium hydroxide 50% liquid

is transmitted by special tanks to caustic soda flakes manufacturing companies.

And then, the liquid caustic soda during the process of production in the condensing lines,

while evaporating the water in it, turns into a solid caustic soda of 98-99%.

Chemical solvents
Chemical solvents

Chemical solvents

Chemical solvents are substances that dissolve other materials
Chemical solvents are generally divided into two groups of polar
solvents and nonpolar solvents
In a polar solvent, the particles form a polar solvent and absorb each other by electrostatic gravity
The most important polar solvent is water
Types of acids such as sulfuric acid H2SO4 and hydrogen fluoride HF are also included in this category
In non-polar solvents,
non-polar solvents are present,
and therefore there is only a weak gravitational force between particles, which is why these solvents often have a very low boiling point and are volatile.
Organic solvents have less polarization than non-organic solvents or mineral solvents, and as a result, these solvents, soluble non-polar

materials better

Types of chemical solvents


Most used in scientific experiments.
Due to its solubility in water and ether,
it can be used in natural resins such as cholate,
PVA, polyvinyl acetate, polyvinyl butyric, resin esters,
ketone resins
As solvent, anti-freeze germicide, fuel, a dull substance in the petrochemical industry, pharmacy


The water molecule (HOH) has both a hydrogen atom and an OH-factor.
So it is both Alkaline and acid, and hence chemically.
Pure water or distilled water dissolves acids,
alkalis, metal salts, herbal gums, strong serum adhesives,
plastic dyes, and alcohols.


Chloroform is one of the best solvents of alkaloids in their base form.
Extracting antibiotics, vitamins, and flavors
Reagent or laboratory detector to detect early amines,  bromides
In decomposition chemistry for the separation of compounds
To keep organic tissues in the lab
Acetone (Propane)
Acetone is used as the solvent for many organic compounds.
In the production of plastics, synthetic fibers, pharmaceuticals and other chemical compounds.
Indigo colors are also used in industrial production

Phosphoric acid

Production of phosphate fertilizers such as oxoammonium phosphate, ammonium phosphate, triple superphosphate
, magnesium phosphate and …

The production of phosphates used in detergents such as trisodium phosphate and sodium tripolyphosphate.

Production of industrial phosphate cleaners:
In the production of acid detergents

Production of purifying and coagulating materials in the water and wastewater industry.

In the form of edible grains, consumption in the food industry:
in the production of acidic foods and carbonated beverages, such as the types of cola

Ethylene glycol

Mono ethylene glycol is used in the plastic industry
, In the production of resins and polymer fibers
In the production of polyester fibers, bottles of beverages and packaging films
In the global production of this product, it produces polyesters of polyethylene terephthalate

Hydrofluoric acid

For engraving on a glass in a lamp
Synthesis of ammonium fluoride from ammonia and hydrogen fluoride reactions
In the manufacture of decorative crystals and matte glassware
The steel industry, ceramics,
casting, furnace and alloys and so on …
The production of uranium and more than one hundred fluorinated chemicals


Xylene is one of the important solvents that are the main components of crude oil.
In the adhesive industry to reduce the viscosity
In the production of waterproof coatings and pipeline lines
Washing of transport equipment includes cleaning of trucks, railway rails, multipurpose containers of aircraft tanks, old dish

Other chemical solvents

Dimethyl sulfoxide

DMSO is a sulfur compound that is a natural and anti-inflammatory agent.
Dimethyl sulfoxide is used to treat amyloidosis and palmar and leg syndrome.


The main application of DMF is its use as a solvent with a low evaporation rate in various industries.
Other uses:
For example, in the production of acrylic and plastic fibers In the manufacturing industry of the label, synthetic leather, fibers, films and surface coatings Suitable catalyst for halide acid production

Ethyl acetate

The main uses of ethyl acetate in the manufacture of nitrocellulose and cellulose acetate, lacquer and as a solvent component in glue and in the expansion compositions for artificial leather.
Other uses:


In caffeine extraction from coffee and tea, in the food industry (sweets) as essential oils
In perfumery as a solvent


Pentane is one of the most volatile hydrocarbons at room temperature. Pentane is often used as a solvent that is easily evaporated. Since pentane is non-polar, only non-polar materials are dissolved in it.
Pentane is also one of the common fuel components. Pentane is used as a foaming agent in foam polystyrene production. Pentane is used in geothermal force units.


Solvent, anti-icing agent and in the preparation of other chemical compounds
Limited as a fuel in engines with an internal combustion system


The solvent in the pharmaceutical industry,
for resins and cellulose esters and in the fermentation process
In the printing industry
As an antiseptic for cleaning the skin before surgery

Continue chemical solvents …


Of normal butanol to produce butylated acetate, butyl acrylate, DE butyl phthalate and butyl ethers, etc.

Production of polymers, pharmaceuticals, herbicide esters and so on…

Additives in perfumes and auctions in the extraction of certain oils


Heptane and its isomers are widely used in solvents for laboratories.
In the test of the spot test, heptane is used to dissolve the oily specimen to show the number of organic compounds present in it.

Extraction from heptane means identification of bromine solutions from iodine.
Heptane is commercially available for rubber and fuel glue.


Converting octanol to ester form, this substance is used as a perfume.
The molecular dispersion of octanol/water,
used in environmental chemistry and pharmacy chemistry to estimate the behavior of a substance, indicates that octanol is a natural substance


The primary use of this polymer is for the manufacture of SanDisk polyurethane fibers such as spandex.
As its main use solvent, it is used as an industrial solvent for PVC and in polishers.

An aprotic solvent with a dielectric constant of 7.6, which is a polar solvent and can solve a lot of polar and nonpolar compositions, is water-immiscible and can be clathrate structures
Form clathrate hydrate with water at low temperature.


Sulfate is used to extract aromatic compounds.


Toluene (Methylbenzene or Phenyl methane) is a liquid that is insoluble in water with a similar odor to conventional odor thinners.
Toluene is a group of aromatic compounds and is used as an essential ingredient as well as a chemical solvent.

Other uses include a color solvent, paint thinner,
silicone sealant, chemical reactive agent, plastic, printing ink, glue, varnish, disinfectant, and disinfectant. It can also be used to make foam and TNT.