Measuring the concentration of caustic solutions is a fundamental step in numerous chemical and industrial processes. It involves determining the exact concentration of an alkali in a solution. This is of great importance in order to understand the chemical properties and reaction behavior of the lye and to use it accordingly.
The most common alkalis used in chemistry include Sodium hydroxide (NaOH) , also known as caustic soda, potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂), ammonium hydroxide (NH₄OH), magnesium hydroxide (Mg(OH)₂) and lithium hydroxide (LiOH).
Concentration measurements with LiquiSonic® measuring devices
The LiquiSonic® measuring systems enable inline concentration measurements of alkaline solutions. The measuring technology is able to analyze the components of substance mixtures and can provide information about the concentration or density in real time. The sensors are based on the principle of ultrasonic velocity measurement. They are therefore virtually maintenance-free and can reliably provide measured values even under demanding measuring conditions.
Installation of LiquiSonic® measuring systems
LiquiSonic® sensors can be installed directly in the user's system without a bypass, for example in pipelines. There are also different variants that are tailored to specific areas of application and have special properties.
Applications of concentration measurements
Concentration measurement is one of the essential methods for analyzing the quality and safety-relevant characteristics of products and substances. It therefore plays a decisive role in several industries.
A practical example of the application of concentration measurement can be found in the pharmaceutical industry, where the precise determination of the concentration of active ingredients in drugs is essential to ensure their effectiveness and safety. This shows the importance of precise concentration measurement methods in quality assurance.
Concentration detection is used in the following areas:
Chemical production (to monitor the composition of mixtures)
Pharmaceutical industry (e.g. for the production of medicines)
Food production (to control the quality of food)
Metallurgy (to check the quality of metal ores)
In addition, concentration measurement is also commonly used in other areas within industry and science.
What is a lye solution?
An alkali, often referred to as an alkaline solution, is an aqueous solution containing hydroxide ions (OH-). Lyes are formed by dissolving a base in water and are characterized by their ability to neutralize acids in a neutralization reaction. They often have a soapy feel, can dissolve organic substances such as fats and oils and change color indicators (such as phenolphthalein) in a manner typical of bases.
How do you determine the concentration of an alkali?
The alkali concentration can be determined in various ways. Some common methods are:
Speed of sound measurement: The measurement of the speed of sound in a solution is used to determine the concentration of a caustic solution. This method is based on the fact that the speed of sound in a liquid depends on the density and elastic properties of the solution, which in turn are influenced by the concentration of the dissolved substances. When measuring the speed of sound, a sound pulse is sent through the solution and the time it takes to travel a known distance is measured. The speed of sound can be calculated from this time and distance.
Titration: One of the most common methods for determining the concentration of an alkali is acid-base titration. In this method, the lye is allowed to react with an acid of known concentration up to a neutralization point. The concentration of the alkali can be calculated from the consumption of the acid. Indicators or pH measurements are used to determine the end point of the titration. Titration is time-consuming, manually intensive and can be inaccurate with dilute solutions or in the presence of interfering impurities.
pH measurement: The concentration of strong bases can also be determined by direct measurement of the pH value. As the pH value is a measure of the hydrogen ion concentration and strong bases dissociate completely, the concentration of the alkali can be calculated from the pH value. With weak bases, however, this relationship is not direct and requires more complex calculations.
Conductivity measurement: The electrical conductivity of a solution depends on the concentration of dissolved ions. Therefore, the measurement of conductivity can be used to determine the concentration of an alkali. This method is particularly useful for solutions that are highly ionic. However, it is also sensitive to the presence of different ions, which can lead to inaccuracies, and is complicated to calibrate.
Spectroscopic methods: For alkalis that contain specific absorbing or emitting species, spectroscopic techniques such as UV-Vis spectroscopy can be used to determine the concentration. The intensity of the absorption or emission is related to the concentration of the alkali. These methods require specific absorbing or emitting species in the solution and are unsuitable if such properties are absent or interfered with by other substances.
Applications of alkali concentration measurements
Concentration measurements of alkalis are relevant in various areas and applications. These include, among others: Soap and detergent production, neutralization reactions, pH regulation, synthesis of chemicals, extraction processes, digestion of biomass, waste water treatment & corrosion protection.
