Name: calibrating lab glassware for accurate volume
Uploaded: 2024-12-05T18:31:54.000Z
Duration: 1 min 11 s
Channel: JoVE

Las mediciones de volumen precisas son cruciales para los análisis basados en soluciones. El equipo volumétrico estándar incluye matraces, pipetas y buretas.
Los matraces volumétricos se utilizan para preparar y diluir soluciones para un volumen específico. Están marcados como TC, que significa "contener".
Están calibrados para contener un volumen preciso a temperaturas especificadas, donde el coeficiente mínimo de expansión del vidrio permite un volumen casi constante a pesar de cambios menores.
Las pipetas etiquetadas como TD suministran un volumen específico a una temperatura determinada. Están calibrados para tener en cuenta el drenaje de la película en las paredes de vidrio, que varía con el tiempo de entrega.
Las pipetas volumétricas con la calibración adecuada suministran un solo volumen con precisión de hasta cuatro o cinco cifras significativas. Las pipetas de medición proporcionan diferentes volúmenes con una precisión menor de hasta tres cifras significativas.
Una bureta es un tubo calibrado para sujetar el valorante que se puede dispensar con precisión a través del sistema de válvula manual para controlar el flujo del valorante.

calibración de material de vidrio

La calibración precisa de material de vidrio, como matraces volumétricos, pipetas y buretas, es esencial para garantizar mediciones precisas en el laboratorio analítico. La calibración ayuda a mantener la coherencia en las mediciones y evita errores que surgen de volúmenes imprecisos. Matraces volumétricos

Los matraces volumétricos están diseñados para preparar soluciones acuosas de volúmenes precisos con precisión, con una línea de calibración en el cuello. Para calibrar un matraz volumétrico, es importante llenarlo con agua destilada hasta que el menisco (la superficie curva del líquido) se alinee con la marca de calibración. Ver el menisco a la altura de los ojos garantiza lecturas precisas. La calibración se realiza normalmente a una temperatura específica (~20 °C) para tener en cuenta el efecto de la temperatura en el volumen. Si el nivel del agua está por encima de la línea, escúrralo con cuidado hasta que llegue a la marca; si la línea de agua está por debajo, agregue más agua gota a gota hasta que llegue a la marca. Después de la calibración, la capacidad del matraz se puede confirmar pesando el agua y comparándola con el valor teórico en función de su densidad.

Pipetas

Las pipetas se utilizan para transferir volúmenes específicos de líquido.

Pipetas volumétricas: están diseñadas para suministrar un volumen único y de gran precisión, normalmente de cuatro o cinco cifras significativas. Para la calibración, primero se limpia y enjuaga la pipeta con la solución que se va a medir, se llena hasta la marca de calibración y se deja que se vacíe por completo en un recipiente. A continuación, se comprueba la precisión pesando el agua suministrada y comparándola con el volumen teórico basado en la densidad del agua.

Pipetas graduadas: a diferencia de las pipetas volumétricas, las pipetas graduadas están marcadas con una serie de líneas y pueden suministrar múltiples volúmenes, pero con una precisión ligeramente inferior, generalmente de hasta tres cifras significativas. El menisco también debe observarse cuidadosamente durante la calibración y la medición.

Bureta

Una bureta es un tubo de vidrio largo y graduado con un grifo en un extremo que dispensa con precisión cantidades variables de una solución, en particular en titulaciones. Al calibrar una bureta, asegúrese de que el menisco esté correctamente alineado con las marcas antes y después de la titulación, y verifique que el volumen dispensado sea el esperado comparando el peso del agua suministrada con su valor teórico. El depósito de la bureta contiene marcas para indicar el volumen del líquido. La llave de paso o grifo en la parte inferior sirve como válvula manual que permite a los usuarios controlar el flujo de líquido desde el depósito, lo que permite una medición precisa de la cantidad dispensada.

Otros materiales de vidrio

Otros tipos de material de vidrio de laboratorio, como los cilindros graduados, también se utilizan comúnmente para mediciones de volumen, pero ofrecen una precisión menor que el equipo volumétrico. Por lo general, proporcionan volúmenes de hasta tres cifras significativas, adecuados para trabajos menos precisos. Sin embargo, la calibración de estos elementos sigue siendo importante para mantener la confiabilidad de la medición.

La calibración del material de vidrio de laboratorio garantiza mediciones precisas y confiables, lo cual es crucial para mantener la integridad de los resultados analíticos. Ya sea que se utilicen matraces volumétricos, pipetas, buretas u otro material de vidrio, las técnicas de calibración adecuadas ayudan a prevenir errores y mejorar la precisión del trabajo de laboratorio.

Calibración de material de vidrio

La calibración precisa de la cristalería, como matraces volumétricos, pipetas y buretas, es esencial para garantizar mediciones precisas ...

Education

Educación

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidad 1

Method Development and Sampling Techniques

Desarrollo de Métodos y Técnicas de Muestreo

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Glassware Calibration

calibrating lab glassware for accurate volume

Calibrating lab glassware helps students measure liquids accurately in the analytical laboratory. It reduces volume errors and supports consistent results across measurements. This matters when using volumetric flasks, pipettes, burettes, and other tools that depend on precise volume readings.

Volumetric flasks are used to prepare aqueous solutions with a precise final volume. They have a calibration line on the neck. To calibrate one, fill it with distilled water until the meniscus, the curved surface of the liquid, lines up with the mark at eye level. This is usually done at about 20°C because temperature can affect volume. If the water rises above the line, drain it carefully. If it is below the line, add water drop by drop until it reaches the mark. The flask’s capacity can then be checked by weighing the water and comparing it with the theoretical value from its density.

Pipettes are used to transfer set amounts of liquid. Volumetric pipettes are made to deliver one highly accurate volume, often to four or five significant figures. To calibrate one, clean it and rinse it with the solution to be measured, fill it to the calibration mark, and let it drain completely into a container. The volume delivered is checked by weighing the water and comparing it with the theoretical volume based on water density. Graduated pipettes have a series of marks and can deliver different volumes, but they are slightly less accurate. They are generally used to about three significant figures, so the meniscus must still be read carefully.

Burettes are long, graduated glass tubes with a tap at one end. They are used to dispense variable amounts of solution, especially during titrations. When a burette is calibrated, the meniscus must be aligned with the markings before and after use. The volume dispensed is then compared with the expected value by weighing the water delivered. The reservoir shows the liquid level, and the stopcock, or tap, acts as a manual valve that controls flow for precise measurement.

Other glassware, such as graduated cylinders, is also used for measuring volume. These tools are less accurate than volumetric equipment, but they are still useful for work that does not need the highest precision. They usually measure up to three significant figures. Even so, calibration remains important for reliable measurements in the lab. Careful calibration of lab glassware helps protect the accuracy and integrity of analytical results.

Calibrating Lab Glassware for Accurate Volume

calibrating-lab-glassware-for-accurate-volume

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How Analytical Methods Are Checked

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Measuring Analyte Concentration

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Calibrating Lab Instruments for Accurate Results

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glassware calibration

Calibrating lab glassware helps students measure liquids accurately in the analytical laboratory. It reduces volume errors and supports consistent results across measurements. This matters when using volumetric flasks, pipettes, burettes, and other tools that depend on precise volume readings. Volumetric flasks are used to prepare aqueous solutions with a precise final volume. They have a calibration line on the neck. To calibrate one, fill it with distilled water until the meniscus, the...

standard solutions

Preparing Standard Solutions in the Lab

Standard solutions are prepared to have a precisely known concentration or composition. In analytical chemistry, this accuracy is important because it supports reliable results. A primary standard is a highly pure, stable substance with a high molar mass. It is fully soluble in water, which is the most commonly used solvent in analytical chemistry. A primary standard solution can be used to standardize a secondary standard. Secondary standards have known concentrations, but they are usually...

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Blank Solutions in Analytical Testing

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sample preparation for analysis: overview

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sample-preparation-for-analysis-advanced-techniques

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Sample Transport and Storage Basics

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Sampling Errors in Sample Preparation

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key terms and concepts

Learn how volumetric flasks, pipettes, burettes, and graduated cylinders are calibrated to improve volume accuracy, consistency, and lab reliability.

Calibrating Lab Glassware for Accurate Volume | JoVE K12

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Calibrating Lab Glassware for Accurate Volume

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