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Friday, October 29, 2021

What is litmus paper and how does it work

Indicators are a type of chemical that can change color as pH levels change. Several indicators are used in chemistry, including pH paper, universal indicator, and litmus paper (blue or red). These are the rapid and most simple methods for determining pH compared to pH meter whether a sample is liquid or gaseous.

The pH (potential of Hydrogen) value is used to express the concentration of hydrogen in a solution. The pH scale has a range of 0 to 14 and corresponds to the negative logarithm of hydrogen ion concentration.


An acid is a substance that donates hydrogen ions, therefore when there are more hydrogen ions in a solution than hydroxide ions, it is acidic.

A base is a substance that accepts hydrogen ions, therefore when there are more hydroxide ions in a solution than hydrogen ions, it is alkaline.


What is litmus paper in chemistry?

Litmus paper is a type of indicator that comes in the form of a paper strip and is used to determine whether a sample solution is acidic or basic. It is made by mixing water-soluble dyes that are absorbed into the filter paper strips. It is impregnated with lichens, which gives it the capacity to change color when exposed to an acid or base.
“Litmus paper is defined as; it is a strip of paper impregnated with litmus, which is used as a chemical indicator”
Litmus paper is widely used in science classes and practicals, and because of its wide recognition, it has also become a cultural reference in our society.

History of litmus paper:

The word "litmus" is derived from a Norse word that means "dye" or "color." Around 1300 AD, the Spanish physician Arnaldus de Villa Nova first used litmus paper. Originally, litmus was a blue dye produced by a variety of lichen species of the Netherlands. However, litmus can have 10 to 15 different dyes.

What is litmus paper made of?

As the name suggests, litmus paper is primarily composed of paper. Wood cellulose, lichens, and adjunct compounds are the basic raw materials used to formulate litmus paper. 

The paper used to compose litmus paper must be free of contaminants, as that can affect the pH of the sample being tested. Litmus paper, like most other types of paper, is made from the cellulose of wood.

Manufacturing process of litmus paper:

  • Before the paper making process, wood is treated with solvents to remove resinous substances and lignin. Litmus paper provides many features with manufacturing paper production.
  • In this method, the wood pulp is converted into paper, which is then infused with the lichen solution, dried, and packed.
  • Many industries in the market manufacture litmus paper and pH paper, with a different quality that you can buy at different prices.

Types of litmus paper:

Red and blue are two types of litmus paper. Blue litmus paper is used to check for acidity (acidic pH) of the solution; while red litmus paper is used to check for basicity (basic pH) of the solution

Red litmus paper:

What is litmus paper and how does it workRed litmus paper consists of a weak-diprotic acid which purpose is to determine the basicity.  When it is exposed to the basic or alkaline substance, a reaction happens between hydrogen ions and a base that produces a color change which changes to blue. 
However, if it comes into contact with an acidic or neutral solution, it will remain red.

Blue litmus paper:

What is litmus paper and how does it workBlue litmus paper already consists of a blue conjugate base and is used to determine the acidity. When it is exposed to the acidic substance, it reacts with acid and that produces a color change which changes to red. 
However, if it comes into contact with a basic or neutral solution, it will remain blue.

How litmus paper works (Mechanism):

  • Red litmus contains a weak diprotic acid. The hydrogen ions react with the added base when it is exposed to a basic compound. The conjugate base formed from litmus acid is blue; therefore wet red litmus paper turns blue color in alkaline solution. 
  • On the other hand, blue litmus paper already contains a blue conjugate base. When it comes into contact with an acid, it becomes red.
  • In addition, blue litmus paper can indicate an acid that has a pH level of about 04 to 05 or less. Similarly, red litmus paper may indicate a base that has a pH level greater than 08. However, if a sample solution has a pH of 05 to 08; it indicates a minute change in color on paper.

How to perform litmus test:

  • The litmus test is performed by placing a drop of liquid sample on a strip of paper or immersing a piece of litmus paper in a sample. Ideally, it is not recommended to immerse the litmus paper in the entire container of a sample solution, as the dye can potentially contaminate the samples.
  • Litmus paper can be moistened with distilled water to change the color of the gaseous sample. The gases sample changes the color of the entire litmus strip when the entire surface is exposed.
  • Litmus paper that has changed color from red to blue can be used again as blue litmus paper. Litmus paper that has changed color from blue to red can be used again as red litmus paper.
The table shows how the color of litmus paper changes in different solutions.
Condition Red litmus Blue litmus
In acidic solution Remains Red Turns red
In neutral solution Remains red Remains blue
In alkaline solution Turns blue Remains blue




Advantages of litmus paper:

  • Litmus testing is a simple and cost-effective procedure that does not require a trained person or the use of expensive equipment.
  • It is a fairly simple acid-base indicator that provides accurate results.
  • It quickly determines the nature of the substance compared to other methods of pH determination.
  • Litmus paper is used for both liquid and gaseous samples.

Disadvantages of litmus paper:

  • Like a pH indicator, pH meter, or pH paper, it does not determine the strength of the sample.
  • If it is immersed in the sample solution, it can contaminate them.
  • It is a one-time use item that may have issues with the reproducibility of results.


FAQ (Frequently Asked Questions):


What are the use of litmus paper and pH paper?
Litmus paper and pH strips are used in chemistry to determine the acidity or alkalinity of a sample solution. Litmus paper simply states whether a solution is acidic or alkaline, while a pH paper determines the pH value of a solution.

What does it mean when litmus paper is blue?
This means that the pH of the sample is alkaline.

What is the difference between blue and red litmus paper?
The reactivity to different pH values is the major difference between them; blue litmus paper reacts to acidic samples, with red litmus paper reacts to alkaline samples.

How does litmus paper indicate an acid?
Litmus paper is a filter paper that turns red in acidic solution and blue in alkaline solution.

Litmus paper is an example of what?
Litmus paper is an example of an organic indicator; it is a chemical substance that changes color when exposed to acids or bases, for example, Sodium hydroxide (NaOH), and Hydrochloric acid (HCL).
 
 

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Thursday, October 28, 2021

Difference between blue and red litmus paper

The major difference between red litmus paper and blue litmus paper is that their reaction to different pH values, the blue litmus paper reacts to acidic samples, while red litmus paper reacts to alkaline sample solutions.

Indicators are a particular type of chemical, which can change their color when changing pH. In chemistry there are several indicators are used such as universal indicator, pH paper, and litmus paper (blue or red), etc. these are the fastest and easiest way to determine pH.

Definition of litmus paper:

It is a type of paper, when it is immersed in a solution, it changes color according to the acidity of the solution.

What is litmus paper?

The litmus paper is an indicator which available as a paper strip and it is used to detect the acidic and basic of sample solutions. It is made by a mixture of water-soluble dyes which are absorbed into the filter paper strips.
Difference between blue and red litmus paper

There are two types of litmus paper available which are blue and red color. Alkalinity is measured using red litmus paper, while the acidity is measured using blue litmus paper.

Around 1300, a Spanish physician named Arnaldus de Villa Nova used litmus for the first time. From the 16th century onwards, the blue dye was extracted from lichens in the Netherlands.

The basic raw ingredients used to make litmus paper are lichens, wood cellulose, and adjunct compounds. Litmus paper is made of paper that must be free of pollutants, as this can affect the pH of the sample being tested.

Red litmus paper:

As the name suggests, red litmus papers are colored red. The red litmus paper becomes blue when contacting with the basic or alkaline sample, it is used only to test for basic pH level. It will remain red if it comes into contact with an acidic or neutral solution.

Blue litmus paper:

As the name suggests, blue litmus papers are colored blue. The blue litmus paper becomes red when contacting with the acidic sample, but, if a substance is basic or neutral, then it will remain blue. It is used only to test for acidic pH levels.

Difference between red and blue litmus paper:

  • The major difference between red litmus paper and blue litmus paper is that their reaction to different pH values, the blue litmus paper reacts to acidic samples, while red litmus paper reacts to alkaline samples.
  • Red litmus paper is used to test alkalinity, while blue litmus paper is used to test acidity.
  • The color of red litmus paper is red, while the color of blue litmus paper is blue.
  • When red litmus paper comes into contact with acid, it remains red; when blue litmus paper comes into contact with the base, it remains blue.
  • Red litmus paper remains red, while blue litmus paper remains blue when it comes in contact with a neutral substance.
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What is the difference between the litmus paper and universal indicator?

The pH is a significant factor that determines whether a solution is acidic or alkaline. It measures the concentration of hydrogen ions (H +) in the solution. pH is measured using a variety of methods, which are chosen depending on the application. It includes pH meter, pH paper, and litmus paper (blue or red), and universal indicator, etc. These are the quickest and most simple ways to determine pH, and each has its own advantage.


What is litmus paper?

Litmus is a water-soluble mixture of various dyes which is extracted from lichens. It is absorbed onto filter paper to make one of the kinds of pH indicator, which is used to determine the acidity of the sample.

Litmus paper is used to perform the litmus test which determines whether the sample/substance is acidic or basic. It is available in two types of strips, which are red and blue, and works similarly to pH paper. The red litmus paper turns blue if the sample has an alkali, whereas in acids the blue litmus paper becomes red. In neutral, both litmus papers do not change their color if the sample is neutral.

What is a universal indicator?

A universal indicator is a mixture of dyes that begin with green color, but while added to a solution it changes color. The color that changes, not only specifies that the substance is acidic or basic, but it can show the position on the pH scale from 0 to 14. Colors ranging from yellow to red specify an acidic solution, blue to violet indicate alkali, and green indicates a neutral solution.

Difference between the litmus paper and universal indicator:

  • The major difference between the litmus paper and the universal indicator is that the universal indicators can change a range of various colors, so it is useful in determining the strength of an acid or base, while the litmus paper only gives you an indication of whether the substance is an acid or alkali; it doesn't tell us about the strength of the acid or the base.
  • Litmus paper is used in tests where only the acidic or basic nature of the substance is involved, while the universal indicator is used in tests were to know the pH of a substance.



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Wednesday, October 27, 2021

Difference between pH meter and pH paper

The major difference between the pH meter and pH paper is that the pH paper used to determine the pH is not as accurate as a pH meter, which determines the exact pH of the sample.

The pH is an important factor that specifies the acidity or alkalinity of the solution it measures the hydrogen ions (H +) concentration in the solution. The pH determines by the various method in which the electrometric method and colorimetric method are used. Universal indicator, pH meter, pH paper, and litmus paper (blue or red), etc. are the fastest and easiest way to determine pH.

What is a pH meter?

The pH meter is an electronic apparatus that is utilized to determine the pH of the sample solution. It has an electrode (glass electrode or reference electrode) attached to the meter, which can usually measure the small voltage. Since, it is calibrated with standard buffer solutions such as pH 07, pH 04, and pH 09.20, it gives accurate results on a scale of pH 0 to 14.

It is also referred to as a potentiometric pH meter since it measures the difference in electric potential between a pH electrode and a reference electrode. Depending on the pH level, a color-changing indicator, pH paper, or litmus paper can be used to get an approximate pH of the sample. The precision of such types is limited, and it can be complex to interpret correctly and hence a pH meter is most widely used to determine the pH of a sample solution.

What is a pH paper?

A pH paper is a piece of paper that is used to determine the pH of a solution and comes as strips that are saturated with pH indicators. It changes color when it comes into contact with the sample solution being tested, according to the pH of the sample solution.

It is a quick, simple, and reliable way of measuring acidity or alkalinity. Usually, a drop of the solution can be placed on the pH strip or it is immersed in the solution to see the color change compared to the reference scale (01-14).

Difference between pH meter and pH paper:

  • The major difference between a pH meter and a pH paper is that the paper used to determine the pH is not as accurate as a pH meter, which determines the exact pH of the sample.
  • As the name suggests, a pH meter is an instrument while pH paper is a paper strip.
  • The digital pH meter records pH values continuously and repeatedly and even allows automatic recording of measurements, whereas the paper strip can be used for only one manual measurement.
  • A pH meter requires more sample quantity to immerse the electrode, while a pH paper requires only a drop to detect a color change.
  • A pH meter is an expensive method of determining the pH of any solution as compared to paper, while a pH paper is an economical method as compared to a pH meter.
  • The readings provide by a pH meter are accurate and reproducible, while test strip results can vary depending on how the strips are handled, Different people perceive colors differently and may interpret color comparison in different ways.
  • pH meter has a longer shelf life, whereas pH paper has a shorter shelf life, test strips contain reagents that degrade over time.
  • pH meters require regular maintenance and calibration, which is time and cost consuming, while pH paper saves time and cost.
  • A pH meter apparatus that can provide computerized digital data in the form of software or printers and is recommended for audit and regulatory compliance, whereas the results provided by strips are not acceptable for that purpose.
  • Generally, a pH Meter is chosen instead of a pH Test strip since a pH meter often gives better resolution than the pH strips, and it is normally considerably more exact and accurate than test strips.

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Tuesday, October 26, 2021

Difference between pH paper and litmus paper

Solutions and chemicals are often categorized as basic, acidic, and neutral. These classifications are decided on the pH scale (pH 0 to 14). Acidic has a low pH value, basic has a high pH value, and neutral has around 7 pH. The measurement of pH is an important factor in every field. It is widely used in agriculture to maintain the quality of water, soil, and pesticides, as well as for medicinal, pharmaceuticals, research, production, and quality control since it affects most of the product and quality.

There are different types of methods are available to determine the pH value of the substance in which the electrometric and colorimetric methods are used. Some of the commonly used methods of pH determination are universal indicator, blue litmus paper, red litmus paper, and pH paper, etc.
Difference between pH paper and litmus paper

What is pH paper?

A pH paper is a piece of paper (indicator) that is used to determine the pH of a solution, which is come in the form of strips that have saturated with pH indicators. Thus whether acid or a base is present; pH paper can change its color according to the pH of the sample solution.

Generally, it is used by immersed in the solution, or a drop of the sample solution can be placed on the strip of pH to view the change of color. The color is compared to the reference scale (01-14) when a color change occurs. This method is used to find the pH of a solution.

What is litmus paper?

A litmus paper is a test strip that is used to determine whether a sample solution is acidic or basic. Litmus paper is devoid of impurities that can cause color change due to the pH of the solution. Lichen is the primary raw material used in the manufacture of litmus, and paper becomes pH activated after a lichen infusion.

Litmus paper comes in two types: red and blue. The color of red litmus turns to blue when a drop of basic solution is placed on it, and when a drop of a basic solution is added to blue litmus, its color does not change. The color of red litmus paper will not change if an acidic solution is dropped on it. On the other hand, a drop of acidic solution on blue litmus changes the color from blue to red. As compared with the pH paper, litmus paper is unable to provide an accurate pH value for a solution.

Difference between pH paper and litmus paper:

  • The major difference between the pH paper and litmus paper is that the litmus paper shows that the sample is acidic or basic or neutral, whereas the pH paper gives the exact value of pH.
  • The pH paper has a scale that ranges from 01 to 14 and is used to determine the acidity or alkalinity of a solution, whereas litmus paper gives and a rough idea of whether a sample solution is acidic or basic.
  • pH paper gives more accurate readings than litmus paper.
  • Depending on the pH of the solution, pH papers provide a range of different colors, whereas litmus paper only shows two colors, red or blue.
  • pH strips are thought to be more sensitive than litmus paper, as litmus paper cannot provide quantitative data.



FAQ (Frequently Asked Questions):


Which is more accurate pH paper or litmus paper?
pH paper gives more accurate results than litmus paper because pH paper can determine the pH range of the solution.

Why is universal pH paper better than litmus paper?
Because a universal pH paper may indicate a variety of colors based on the pH of the solution, hence it is useful for determining the acid or alkali strength.

Is pH paper litmus paper?
Litmus paper is a type of pH paper, both of which are used in different ways to determine whether a sample solution is acidic or basic.


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Difference between pH paper and universal indicator

Generally, the blue litmus paper, red litmus paper, pH paper, universal indicators, and pH meter are used to determine the pH. The pH paper is an indicator that changes as per the substance, in which it is dipped, Although a universal indicator is a liquid/solution substance that is dropped into a sample and it changes the substance as per the pH (acidic or basic).

The range of pH is between the pH 0 to pH 14 scale, in which below pH 07 is considered as acidic, above pH 07-14 is considered basic and pH 07 is neutral, it depends on the concentration of hydrogen ions which present in the substance.

What is pH paper?

A pH paper is a piece of paper strips are saturated with a pH indicator, it is used to determine if a solution is basic, acidic, or neutral. It is determined by dipping a piece of paper in the solution and its color changes according to the pH.
The chemical flavin causes a pH paper to change color in different solutions. This anthocyanin molecule is soluble in water and changes color when exposed to different types of liquids.

What is a universal indicator?

A universal indicator is a combination of various indicators that displays a range of colors depending on the pH of any sample solution. It comes in two types: a liquid ethanol solution and a pH paper soaked in an indicator solution.

Difference between the pH paper and universal indicator:

The major difference between the pH paper and universal indicator is the pH paper gives the exact pH of the substance, whereas the universal indicator is used to find out whether it is acid or alkaline, or neutral.


FAQ (Frequently Asked Questions):


Is universal indicator and pH paper the same?
The universal indicator and pH paper both are different things; however, they are used for the same purposes, which interprets how acidic or basic a solution is.

Why pH paper is called a universal indicator?
pH paper is known as a universal indicator, as it exhibits diverse colors at various concentrations of hydrogen ions in a solution. A universal indicator may exist in paper form or as a solution.

What is the difference between a universal indicator and a pH meter?
A pH meter is a device that measures pH digitally using a probe (Electrode) and voltmeter, while a universal indicator is a mixture of color-changing indicators that represent the pH of a solution.
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Monday, October 25, 2021

Advantages and disadvantages of glass electrode

The pH is the concentration of hydrogen ion in the sample, it is the most essential parameter for every solution and formulation. The pH value is significant in chemistry that is used to determine whether the sample is acidic, basic or neutral in nature. Basically, the pH value 07 is neutral, below pH 07 is acidic and 07 to 14 is basic in nature. The pH is measured by a device called pH meter, which contains electrodes, temperature sensors, and indicators or screen.


What is a glass electrode?

Advantages and disadvantages of glass electrodeA glass electrode is an ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion. pH measurement is the most typical application for ion-selective glass electrodes. 

The pH electrode is an example of a hydrogen ion-sensitive glass electrode. Glass electrodes are an essential component in the instrumentation for chemical analysis and physicochemical research.

Advantages of glass electrode:

  • The glass electrode is most generally used where the chemical inertness is essential.
  • The glass electrode is very sensitive.
  • It is used for several kinds of applications.
  • Easy and convenient to use for cleaning and calibrating with a standard buffer solution.
  • It covers an acidic range and an alkaline range of pH.

Disadvantages of glass electrode:

  • Generally, the potential of the glass membrane depends on the pH.
  • It is tedious to accurately determine its single electrode capacity because it depends on many factors.
  • Deposits on the membrane of the electrode can disturb the pH measurement.
  • Probability of fragile glass breakdown.
  • The electrode is often needed to calibrate.
  • The special types of buffer solutions are necessary to calibrate.

Advantages of calomel electrode:

  • There is no need for a separate salt bridge because it already contains a side tube with a KCL (Potassium chloride) solution.
  • The electrode potential is repeatable and consistent.
  • They are convenient, compact, and relatively low cost.

Advantages of standard hydrogen electrode:

  • It may work as both an anode and cathode half cell.
  • Because a very minimal potential is created on the hydrogen electrode, its electrode potential can be taken to be zero.

Advantages of silver/silver chloride electrode:

  • It is simple and inexpensive to prepare.
  • Its results are stable and sturdy.
  • It covers a broad range of samples.
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Sunday, October 24, 2021

Principle of Karl Fischer Titration

Learn about the principle, types, and applications of Karl Fischer titration, which is a commonly used titrimetric method for the determination of water, or moisture in different types of samples including solid, liquid, and gas.

What is Karl Fischer titration?

Karl Fischer titration is a titration technique that determines the amount of water contained in a given sample of analyte by using volumetric or coulometric titration. Karl Fischer, a German scientist, discovers this method for quantitative chemical analysis in 1935. Nowadays, The Karl Fischer titrator is a modern automated apparatus that can execute such titrations.

It is a commonly used titrimetric method for the determination of water in different substances. Water determination is significant to ensure product quality and to assure the chemical and physical properties of the product.

For example, in the pharmaceutical industry, the stable content of water is very significant for intermediate powders and granules, by which tablets are prepared. The content of water that is too high or too low reduces the effectiveness of pharmaceutical / medicinal products.

Principle of Karl Fischer titration:

The oxidation process between sulphur dioxide and iodine is the basis for Karl Fischer titration. The chemical equation for the reaction of iodine, sulphur dioxide, and water which is used throughout Karl Fischer titration is explained below.

I2 + SO2 + H2O → 2HI + SO3

Sulphur trioxide (SO3) and hydrogen iodide (HI) are formed when water (H2O) reacts with iodine (I2) and sulphur dioxide (SO2). This basic reaction uses exactly one molar equivalent of water vs. iodine. 

Iodine is gradually added to the solution until it reaches an excessive level, indicating the titration's endpoint, which is detected using potentiometry. The reaction is performed in an alcohol solution containing a base, which consumes the generated hydroiodic acid and sulphur trioxide.

Bunsen reaction Karl Fischer titration:

The basic principle behind Karl Fischer titration is based on the Bunsen reaction between iodine (I2) and sulphur dioxide (SO2) in an aqueous medium. Karl Fischer found that this reaction could be modified to determine the amount of water in a non-aqueous method with an excess sulphur dioxide concentration. He employed pyridine as the buffering agent and a primary alcohol (methanol) as the solvent.

Principle of Karl Fischer Titration


The alcohol reacts with SO2 and a base to form an intermediate alkylsulfite salt, which is subsequently oxidized to an alkylsulfate salt by iodine. Water is consumed in this oxidation process.

Different physical and chemical methods are used for determining the content of the water. Of these, the KF titration method has been recognized as a reference for general use. It is described by its high accuracy and specificity workings on a broad range of concentrations from 100% to PPM.

Types of Karl Fischer titration:

Volumetric Karl Fischer titration and Coulometric Karl Fischer titration are the two types of techniques that are used for the determination of water content by Karl Fischer.

Volumetric Karl Fischer titration:

In a volumetric titration, iodine is mechanically introduced into a solvent containing the sample throughout the titration by the titrator’s burette. The volume of KF reagent consumed is used to calculate the amount of water consumed. 

This method is used to determine the amount of water content in the range of 100 ppm to 100%. One-component volumetric KF and two-component volumetric KF are the two major types of volumetric KFT reagent systems.

Coulometric Karl Fischer titration:

In a coulometric titration, the titrant is generated electrochemically in the titration cell and the endpoint is detected electrochemically. The anodic oxidation of iodide from the solution provides the iodine necessary for the KF reaction. 

The colorimetric method measures the water level much less than the volumetric method. Conventional, or fritted-cell, coulometric KF, and fritless-cell coulometric KF are the two major types of coulometric KFT reagent systems:

Procedure of Karl Fischer Titration:

There are two ways to perform the Karl Fischer titration experiment: Volumetric determination and Coulometric determination.

Requirements:
Karl fisher reagent, dry methanol, and Karl fisher titrator instrument, etc.

Volumetric titrator works on the following three major steps.

  1. Using a burette, it dispenses the iodinated KF titration reagent into the cell.
  2. The titration's endpoint detects using a double-platinum pin indicator electrode.
  3. It calculates the final result based on the amount of Karl Fischer reagent dispenses using the onboard microprocessor.

Coulometric Titrator works on the following three major steps.

  1. This titration generates iodine at the anode of the titration cell, rather than delivering the reagent as in a volumetric titration.
  2. The titration's endpoint detects using a double-platinum pin electrode.
  3. It calculates the final result based on the total charge passed, in Coulombs, using the onboard microprocessor.

Applications of Karl Fischer titration:

  • It is most commonly used in the pharmaceutical industries to detect water content and maintain the quality and shelf life of the product
  • It is used in the oil industry, to detect the presence of water in products, such as brake oil, transformer oil, kerosene, etc.
  • It is used in the food industry since water observation is necessary at different stages of the products.
  • The Karl Fischer titrator is used in cosmetic manufacturing to determine the amount of water in different products such as lipstick, shampoos, creams, and toothpaste, etc.
  • It is the most important and commonly used technique in different industries such as are chemical, power stations, plastics, gases, paper, wood, silk, wool, paints, and adhesives, etc.

Advantages of Karl Fischer method:

  • It provides very accurate and rapid results.
  • It is appropriate for solid, liquid, and gaseous samples.
  • It works with volatile and non-volatile substances.
  • It requires a small amount of sample and has a wide range of determination from 0.001 to 100% or ppm to ng level.
  • The availability of the two different methods expands the versatility of the application range.

Preparation of the KF Reagent:

  • Take 670.00 ml of methanol and 170.00 ml of pyridine using a measuring cylinder.
  • Then accurately weigh 125.00 gm of iodine and pour into the solution and cool it.
  • Then pour 100.00 ml of pyridine into a 250.00 m cylinder, keep the solution in an ice bath and pass in dry sulphur dioxide till its volume reaches 200.00 ml.

Instrumentation of Karl fisher titrator:

A Karl Fisher apparatus normally consists of automated burette assembly (a gas-tight syringe with Teflon tipped plunger with Luer fitting), a stirrer, titration flask, reagent dropper, detection electrode, silica tube, keyboard, display, and printer output, etc.

The normal environmental operating conditions are as follows.
Operation: Indoor
Temperature: Ambient to 450C
Relative humidity: 05 to 70 %



FAQ (Frequently Asked Questions):


What is KF titration?
Karl Fischer titration is a redox reaction that measures the amount of water in a sample by measuring the amount of water consumed during the reaction. It is the reference method for determining water, as of its precision, specificity, and rate of measurement.

Why methanol is used in Karl Fischer titration?
Karl Fischer titrations employ methanol as a solvent. Because methanol has a higher hydrophilic than other alcohols and is a more polar solvent hence the analytes dissolves quickly in it.

How do you calculate the Karl Fischer factor?
The water equivalence factor F is calculated using the formula 0.1566 x w/v in mgs of H2O per ml of reagent, where W is the weight in mgs of sodium tartrate and V is the volume in ml of reagent.
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Thursday, October 21, 2021

Identification test of copper sulphate

Learn the identification tests of copper sulphate through a laboratory experiment or practical.

Aim:

To perform identification tests of copper sulphate on a given sample.

Reference: Indian Pharmacopoeia (IP) 2010

Requirements:

Glasswares and miscellaneous:
Test tube, measuring cylinder, pipette, glass rod, volumetric flask, beaker, dropper, rubber stopper, test tube stand, test tube holder, and balance, etc.

Chemicals:
Sodium sulphide (Na2S), barium chloride (BaCl2), sodium hydroxide (NaOH), stannous chloride (SnCl2), ammonia (NH3), hydrochloric acid (HCL), and iodine (I2), etc.

Procedure for identification of copper sulphate:

  • Test-1: Take about 50.00 mg of the substance pour in 05.00 ml of water. Then add 01.00 ml of prepared solution of sodium sulphide, by which black precipitate is formed.
  • Test-2: Take about 50.00 mg of the substance pour in 05.00 ml of water, and then add 01.00 ml of ammonia solution. The precipitate was solubilized in excess of NH3 on acquiring a dark blue color.
  • Test-3: Take about 50.00 mg of the substance pour in 05.00 ml of water, and then add 01.00 ml prepared solution of dilute NaOH, by which blue precipitate is formed. In excess reagent, the precipitate is insoluble, and when heated, the precipitate turns black.
  • Test-4: Take about 50.00 mg of the substance dissolved in 05.00 ml of water. Add prepared 01.00 ml of dilute hydrochloric acid and then 01.00 ml of barium chloride solution, a white precipitate is formed.
  • Test-5: Add 00.10 ml of prepared iodine solution to the suspension produced in test-D; the suspension stays yellow however is decolorized by adding SnCl2 solution dropwise. Boil the mixture, no colored precipitate forms.
  • Test-6: Take about 50.00 mg of the substance dissolved in 05.00 ml of water. Then add 02.00 ml of prepared solution of lead acetate produces a white precipitate that is soluble in C2H7NO2 solution and NaOH is produced.

Observations:

  • Test-1: The addition of sodium sulphide solution resulted in the formation of a black precipitate.
  • Test-2: The Initial addition of ammonia solution resulted in the formation of a blue precipitate, which was solubilized in excess of ammonia, resulting in a deep blue solution.
  • Test-3: A white precipitate is created when dilute HCL and barium chloride solution are added.
  • Test-4: A yellow color was formed by adding iodine solution to the suspension, which is obtained in test 3. The addition of stannous chloride solution decolorized the color. Even after boiling the solution, the colored precipitate was not obtained.
  • Test-5: A white precipitate is formed by adding lead acetate to the test solution. After adding ammonium acetate and NaOH, the precipitate was solubilized.

Results:

The given sample complies with the tests 1 / 2 / 3 / 4 / 5 / 6 and does not comply with the tests 1 / 2 / 3 / 4 / 5 / 6 for the identification of copper sulphate as per IP 2010.

It suggests that the given sample is of ………………………...


FAQ (Frequently Asked Questions):


Which indicator is used in the assay of copper sulphate?
Generally, the starch indicator is used in the copper sulphate by iodometry.
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Identification test of calcium gluconate

Learn the identification tests of calcium gluconate through a laboratory experiment or practical.

Aim:

To perform identification tests of calcium gluconate on a given sample.

Reference: Indian Pharmacopoeia (IP) 2010

Requirements:

Glasswares and miscellaneous:
Test tube, measuring cylinder, pipette, glass rod, volumetric flask, beaker, dropper, rubber stopper, test tube stand, test tube holder, and balance, etc.

Chemicals:
Ferric chloride (FeCl3), ammonium chloride (NH4Cl), glacial acetic acid (CH3COOH), hydrochloric acid (HCl), potassium ferrocyanide (C6FeK4N6), and ammonium oxalate ((NH4)2C2O4), etc.

Principle:

  • The first test is the reaction of gluconic acid, which forms a yellow complex FeCl3.
  • In an acidic medium, calcium ions do not react directly with hexacyanoferrate (II) ions, however when ammonium ions are added, a white precipitate forms.
  • When ((NH4)2C2O4 is added to C12H22CaO14, a white calcium oxalate precipitate forms. In weak acetic acid, this precipitate is insoluble; however, it dissolves in strong mineral acids like hydrochloric acid.

Procedure for identification of calcium gluconate:

Test 1: Add 00.05 ml of the ferric chloride test solution to 01.00 ml of a 03 % w/v solution, which produces a yellow color.

Test 2: Add 01.00 ml acetic acid to 05.00 ml 2.0 % w/v solution. The solution stays clear after adding 00.50 ml potassium ferrocyanide solution. Then weigh and add about 50 mg of NH4Cl, a white, crystalline precipitate is formed.

Test 3: Add 00.20 ml of a 2 percent w/v prepared solution of ammonium oxalate to 05.00 ml of a 2.0 % w/v solution to form a white precipitate that is sparingly soluble in dilute acetic acid however soluble in hydrochloric acid.

Identification of calcium gluconate


Observations:

Identification Test

Observation

Inference

Test 1

 

 

Test 2

 

 

Test 3

 

 

Results:

The given sample complies with the tests 1 / 2 / 3 and does not comply with the tests 1 / 2 / 3 for the identification of calcium gluconate (C12H22CaO14) as per IP 2010.

It suggests that the given sample is of ………………………...
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