Learn about the principle, types, applications, advantages, and steps of gravimetric analysis which is a method for determining the amount of analyte based on the mass of a solid.
Analytical techniques such as gravimetric, volumetric, and instrumental analysis are commonly used to determine the quantity of a certain component present in a sample. In an analysis, we use a known amount of a known solute to determine the amount of an unknown compound.
This quantity can be expressed as volume or weight. When it comes to volume, we refer to it as volumetric analysis and when it comes to weight, we refer to it as gravimetric analysis.
What is gravimetric analysis?
Gravimetric analysis is a type of quantitative analysis used in analytical chemistry to measure the mass of an unknown analyte in a sample. Precipitation reactions are employed in this method to separate the target component from a sample, and they can convert a dissolved compound (liquid) into a precipitate (solid) so that we can weigh it.
If the sample contains a combination of solids, they must dissolve it in a suitable solvent before adding a reagent that will precipitate the specific component, which is known as a precipitating agent. Finally, filter and weigh the precipitate.
Example: To determine the amount of solids suspended in the water sample- after a particular volume of water has been filtered, the collected solid particles are weighed.
"Gravitational analysis is a laboratory procedure for quantitative analysis based on the mass of an analyte"
Types of gravimetric analysis:
Volatilization, precipitation, thermogravimetry, and electrodeposition are the four primary methods of gravimetric analysis. These 4 methods differ in sample preparation before weighing the solute. One of the most popular methods of environmental engineering measurement is physical gravimetry.
There are two basic types of these methods, both of which involve changing the phase of the analyte so that it can be separated from the rest of the mixture, resulting in a change in mass.
Volatilization:
It is a type of gravimetric analysis also known as physical gravimetry which involves the separation of components mixture either by heating or chemically decomposing them.
Precipitation:
It is a type of gravimetric method which involves the separation of one or more parts of a solution into a solid using a precipitation reaction. Electrodeposition:
It is a type of gravimetric analysis also known as electrogravimetry; it is a technique for separating and quantifying ions of a particular substance, most commonly a metal.
Thermogravimetry:
Thermogravimetric analysis is a type of thermal analysis that measures changes in physical and chemical properties of materials as a function of increasing temperature or as a function of time.
Principle of gravimetric analysis:
The principle of gravimetric analysis is based on determining the mass percent (%) of an ion in an impure compound of a known amount. Later, it is used to calculate the mass percent of the same ion in a known amount of impure substance.
The following are some of the requirements that must be met for the analysis to be accurate:
- The ion to be studied should be completely precipitated
- The precipitate should be in a pure form
- The obtained precipitate should filter out easily.
Example of gravimetric analysis:
To determine the amount of Ba present in a known sample of BaCl2, sulfuric acid (H2SO4) can be used to form insoluble barium sulfate (BaSO4) complex from a solution of an unknown volume of barium chloride (BaCl2).
This BaSO4 can then be used to determine the amount of barium in the precipitate and then determine the mass percentage of barium in BaCl2. When selecting a precipitating agent, keep in mind that it should form a pure insoluble complex with the compound of interest that can be simply filtered.
The determination of chloride in a chemical is another example of gravimetric analysis.
Steps of gravimetric analysis:
- The ion of interest must be entirely isolated to determine its mass. Ion isolation is accomplished with the aid of precipitation. The following are common gravimetric analysis steps:
- The first step is to make a sample solution with a known weight of the analyte.
- The second step of gravimetry involves the separation of the desired ion or element or radical in pure forms using various separation techniques.
- The third step involves weighing the amount of pure insoluble solute formed after the ion has been separated.
- Calculate the amount of a certain constituent in a sample based on the weight of the substance separated.
STEPS INVOLVED IN GRAVIMETRIC ANALYSIS: |
| Preparation of the sample solution |
| Precipitation process |
| Digestion of the precipitate (or) Ostwald ripening |
| Washing and Filtering the Precipitate |
| Drying and Ignition |
| Weighing the precipitate |
Experimental procedure for gravimetric analysis:
- Fill a weighing bottle enough with the unknown, place the lid on sideways, and dry in the oven. In desiccators, cool it.
- Weigh 0.1 mg of the unknown into a beaker using indirect methods.
- Then, dissolve the unknown.
- To the solution, add a precipitant agent.
- Test for complete precipitation, by dropwise addition of precipitating agent and look for signs of precipitation.
- After that, using the vacuum filtration filter the solution. Dry and weigh the precipitate.
- To determine the mass of the ion being studied, use stoichiometry.
- Finally, divide the mass of the compound by the mass of the unknown to determine % by mass of the compound.
Advantages gravimetric analysis:
- It offers extremely accurate results if the processes are followed carefully.
- It is an absolute method, requiring direct measurement without any calibration.
- The analysis is performed with precision employing sensitive and moderate balancing.
- It's used to calculate the atomic masses of a variety of elements to six-figure precision.
- Gravimetry allows relatively low instrumental error and does not require a series of standards to calculate the unknown.
Applications of gravimetric analysis:
- Gravimetric analysis is a technique for determining the amount of analyte or, more precisely, the ion being studied.
- It is used to determine the inorganic anions and cations.
- It is used to determine SO2, CO2, and iodine.
- It is utilized to calibrate other instruments, as this technology may easily produce exact and widely correct data.
- Determination of plasma volume is one of the most common applications is in biology and medicine.
- It can be used in a variety of industries to analyze the nickel content in stainless steel.
- Gravimetric is used for the determination of chloride.
- It is also used to teach science students with practical experience to understand the concept.
Frequently Asked Questions (FAQ):
What is the difference between gravimetric and volumetric analysis?
Gravimetric and Volumetric both are quantitative methods for calculating the amount of sample in a solution or the purity of a compound, the mass of the analyte is determined by gravity analysis, while the volume of the analyte is determined by volumetric analysis.
What is titration in chemistry and its types?
A titration is a technique for determining the concentration of an unknown solution (Titrand) using a solution (Titrant) of known concentration. The titrant is typically added to a known quantity of the analyte from a burette until the reaction is complete.
Generally, an indicator is used to detect the endpoint or equivalence point. Acid-base, precipitation, complexometric, and redox are the different types of titration.
What is the three theories principle that governs gravimetry?
The essential principles and theories of gravimetric analysis are the law of mass action and reversible reactions, the principle of solubility product, and the common ion effect.
References:
- Wikipedia contributors. "Gravimetric analysis." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 31 Aug. 2021.
- Skoog, Douglas A; West, Donald M; Holler, F James (1995). "5.6". Fundamentals of Analytical Chemistry (Seventh ed.).
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- Principle and steps involved in gravimetric analysis. Pharmaceutical Guidelines. Available Here: