Gravimetric Analysis: Procedure, Advantages and Disadvantages

Gravimetric analysis is a quantitative method for estimating the quantity of a chemical correctly based on the mass of a solid. Gravimetric analysis can be used in a variety of ways including the chemical analysis of ores and other industrial materials, equipment calibration, and elemental analysis of inorganic substances.

• It is used to assess the chemical composition of rocks, minerals, and alloys and to check the quality of raw materials and final products. 
• Gravimetric analysis is used to determine the quantitative amount of a substance present in a sample by measuring its mass.
• This method is based on the principle of conservation of mass.
• The principle states that the total mass of the reactants and products in a chemical reaction remains constant.

Also Read: Chemical Kinetics

Key Terms: Gravimetric Analysis, Analytical Chemistry, Analyte, Compound, Ion, Precipitate, Chemical Reaction

---

Gravimetric Analysis

[Click Here for Sample Questions]

Gravimetric analysis is a method in analytical chemistry that uses mass measurement to quantify the quantity of an analyte (the ion being studied). The masses of two substances containing the analyte are compared in gravimetric studies. Gravimetric analysis works on the basis that the mass of an ion in a pure compound can be calculated and then used to calculate the mass per cent of the same ion in a known quantity of an impure compound. Certain requirements must be satisfied for the analysis to be accurate:

• The ion under investigation must be entirely precipitated.
• The precipitate must be a completely pure chemical.
• The precipitate should be easily filterable.

Gravimetric Analysis of Silver

Also Read:

---

Gravimetric Analysis Principle

[Click Here for Sample Questions]

Gravimetric analysis is based on the principle of mass conservation, which states that the total mass of the reactants and products in a chemical reaction remains the same.

• In gravimetric analysis, a known sample is subjected to a chemical reaction to produce a solid precipitate.
• The precipitate is then separated from the solution by filtration.
• It is then washed and dried to a constant mass.
• The weight of the precipitate is then determined accurately using a balance or similar equipment.
• The amount of the substance in the original sample can be determined using stoichiometry by weighing the precipitate mass.

Gravimetric analysis is an accurate method to determine the purity of a substance, identify unknown compounds, and measure the concentration of specific substances in a mixture. However, it requires careful attention to detail and accuracy during sample preparation and analysis. 

---

Steps followed in Gravimetric Analysis

[Click Here for Sample Questions]

Gravimetric analysis generally involves the following steps:

1. Preparation of a solution having a known weight of the sample
2. Separation of the required constituent
3. Weighing the isolated constituent.
4. Calculating the quantity of a specific constituent in a sample based on the measured weight of the separated constituent.

Also Read:

---

Types of Gravimetric Analysis

[Click Here for Sample Questions]

Gravimetric techniques of analysis are utilised when the weights of reactants and products of chemical reactions are predictable, stable, and represent the presence of constituents necessary in determining identification. Gravimetric analysis is classified into four kinds. 

Precipitation Method

In Precipitation Gravimetry, a known quantity of the substance that is to be analyzed is precipitated from the sample solution using a specific reagent as an insoluble compound.

• Many metals react with negative counter ions in their ionic forms to generate stable precipitates.
• Silver ions combine with chloride, bromide, and iodide to produce stable and highly insoluble salts.
• Calcium precipitates quantitatively with oxalate and may be measured reproducibly at any of three temperature-dependent plateaus: oxalate, carbonate, or oxide.

The reaction for the same is given below:

Ca⁺ (aq) + C₂O₄^2- (aq) → CaC₂O₄ (s)

Ag⁺ (aq) + Cl^- (aq) → AgCl (s)

Volatilization Method

The process of separating components of the mixture by heating or chemically decomposing the sample is known as volatilization gravimetry or volatilization gravimetry.

• The substance to be analyzed is converted into a volatile compound and then heated.
• The residue left is used to determine the mass of the volatile compound. 
• Any volatile molecules are separated by heating or chemical breakdown, resulting in a change in mass that we can measure.

Electrogravimetry Method

Electrogravimetry is a technique for separating and quantifying ions of a material, most often a metal.

• The analyte solution is electrolyzed during this procedure.
• The mass of the cathode is measured before and after the experiment, and the difference is used to compute the analyte mass in the original solution.
• The amount of metal deposited is proportional to the quantity of the metal ions in the solution.

Thermogravimetric Method

The thermogravimetric method is an analytical method used to measure a material's thermal stability and volatile component percentage by measuring the weight change that happens while a sample is heated at a constant pace.

• The thermogravimetric analysis measures the mass of a sample as a function of temperature.
• The data collected can provide valuable information about the composition and properties of the sample.

Also Read: Method of Preparation of Diazonium Salts

---

Example Procedure of Gravimetric Analysis

[Click Here for Sample Questions]

The determination of chloride in a chemical is an example of a gravimetric analysis. To perform a gravimetric analysis, a cation that forms an insoluble compound with chloride must be identified. This substance must be pure and readily filtered as well.

According to the solubility principles, Ag⁺, Pb²⁺, and Hg₂²⁺ create insoluble chlorides. Since silver chloride is insoluble, it can be manufactured pure, and it is easily filtered. It might be used to estimate percent Cl^-.

1. Put enough unknown compound in a weighing bottle with the cap on sideways and dry in the oven. Place in a desiccator to cool.
2. In a beaker, weigh an unknown compound of mass to 0.1 mg using indirect methods.
3. Dissolve the unknown compound.
4. Add a precipitating agent to the solution.
5. Heat the solution on a hot plate to increase the particle size for easier filtration. This is often known as digestion.
6. To check for full precipitation, add a drop of the precipitating agent and examine for any signs of the precipitate.
7. Using vacuum filtration, filter the solution. To ensure that all the precipitate has been transported from the beaker to the filter, use a rubber scraper attached to a glass rod. The precipitate must be transported quantitatively to the filter. If any remains in the beaker, the obtained mass will be incorrect.
8. The precipitate should be dried and weighed.

Also Read: Werner’s Theory of Coordination Compounds

---

Advantages of Gravimetric Analysis

[Click Here for Sample Questions]

Gravimetric Analysis has the following advantages:

• The analysis is exact and accurate when a modern analytical scale is used.
• As filtrates can be tested for completeness of precipitation and precipitates can be examined for the presence of contaminants, the potential causes of inaccuracy may be easily verified.
• It is an absolute approach which involves direct measurement and no calibration.
• The determination could be made with relatively inexpensive equipment.
• It can also be used to calculate the atomic masses of numerous elements with six-figure accuracy.
• It has limited space for mistakes and does not need a set of rules for computing the unknown substance.

---

Disadvantages of Gravimetric Analysis

[Click Here for Sample Questions]

Gravimetric Analysis also has some drawbacks:

• It is a very time-consuming method.
• Gravimetric analysis can enable the analysis of a single element or a restricted set of elements at a time.
• Techniques are frequently intricate, and a slight blunder in a method may often spell disaster for the study.
• Gravimetric analysis is based on mass measurement.

Also Read:

---

Things to Remember Based on Gravimetric Analysis

• Gravimetric analysis is a method for determining the quantity of a substance through weight measurement.
• The method uses the precipitation and subsequent weighing of a solid compound by the reaction of the analyte with a reagent.
• Gravimetric analysis is used for the chemical analysis of ores and other industrial materials, equipment calibration, and elemental analysis of inorganic substances.
• This method is used to assess the chemical composition of rocks, minerals, and alloys, as well as to check the quality of raw materials and final products
• Gravimetric analysis requires careful sample preparation, filtration, and drying to ensure accurate results.