Learn about the Principles of Gravimetry

There are various ways to scientifically measure and analyse chemical substances, such as volumetric analysis, instrumental analysis and gravimetric analysis. The analysis concludes by determining the volume or weight of the substance. When expressed in weight, it’s called gravimetric analysis.

The major principle behind gravimetry is the quantitative measurement of an analyte in its purest and solid state. An analyte is a substance undergoing a chemical analysis. The most common method is precipitation for the analyte to be in its purest and solid form.

Gravimetric analysis

It relies on the comparison of the mass of different compounds in the same analyte. Gravimetric analysis can also be explained as comparing the change in mass of a component with the concentration of mass of the same component in the analyte. Gravimetric analysis is highly accurate as it uses various reactions to achieve the best result.

Principle of Gravimetric analysis

One of the major principles behind gravimetric analysis is that if one can determine the concentration of different components in a pure compound, then the concentration ratio can be used to determine if a given sample is pure or not.

The gravimetric analysis requires certain fixed criteria that need to be fulfilled before the analysis can proceed. The other major principles behind gravimetry are,

• The analyte or ion being studied must be precipitated completely, i.e. they need to be in solid mineral form.
• The analyte precipitated must be pure.
• The precipitate must be easily filterable.

Types of gravimetric analysis

There are four major types of gravimetric analysis they are volatilisation, precipitation, thermogravimetry and electrodeposition. The major differentiating factor between these four types is the extraction or analyte preparation before the measurement of the mass of the compound. The main goal of the analysis is to extract the analyte from the compound; this results in a change of mass in the compound.

Volatilisation 

In this method of gravimetric analysis, the process separates the different components in a compound via the process of heating or decomposition chemically.

Precipitation

In the precipitation method, the components undergo a precipitation reaction which separates part of the solution into a solid form called a precipitate; this precipitate is the analyte in solid form.

• Analyte in liquid form- If the unknown analyte is in liquid form, the reaction allows it to convert into solid form, which is the precipitate formed by the reaction.
• Analyte in solid form- If the analyte is in solid form, a precipitate agent is used to dissolve the solids. Then a reagent is added to this new solution that is specifically reactive to the analyte, which will turn into a precipitate.
• After obtaining the precipitate, the solution is filtered in both cases to achieve the purest solid form of the analyte.

Electrodeposition

This process of gravimetric analysis is usually applicable in metals. It is a unique methodology used to extract the analyte ions from the metal.

Thermogravimetry

In this method of gravimetric analysis, the compound undergoes thermal analysis that accounts for the change in chemical and physical factors of the compound with increasing temperature and time. Using this analysis, the analyte is extracted.

The process of Gravimetric analysis 

The analyte should be extracted in its purest form to acquire the mass. The isolation can be done via the various methods of the process discussed above.

Step 1: A compound with a predetermined amount of analyte is measured. 

Step 2: In this step of gravimetric analysis, the separation of the analyte from the compound in its purest solid form.

Step 3: The analyte’s weight is measured after extraction into the pure solid state.

Step 4: The two masses of the impure compound and pure analyte mass are compared.

Advantages of gravimetric analysis 

The advantages of gravimetric analysis are:

• The results are highly accurate if the procedure is performed carefully.
• This method is not like calibration; therefore, the calculations are whole and have to be taken precisely.
• This method reduced instrumental error significantly in comparison to other processes, and the calculations are very simple.
• The process is able to calculate the atomic masses of six figures accurately.

Applications of gravimetric analysis 

Gravimetric analysis has many real-world applications. For example,

• Monitoring the various pollutants in water, such as lead which, if not monitored, causes lead poisoning.
• The nutritional information in packed foods helps one keep track of their diet and their requirements. You can get an estimate of the level of fat present in your milk.
• To check the purity of various metals such as gold and silver.
• Determination of plasma volume (in the field of biology and medicine).
• Inorganic anions and cations can be identified.
• It is also used for the determination of the chloride levels in an analyte.

Conclusion

The principles of Gravimetry are discussed here in detail. The volume of a substance, when expressed in weight is known as Gravimetric analysis.

Types of Gravimetric analysis are Volatilisation, Precipitation, Electrodeposition and Thermogravimetry.

The process, advantages and applications are discussed in this article.