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

Misure accurate del volume sono fondamentali per le analisi basate su soluzioni. L'attrezzatura volumetrica standard comprende fiasche, pipette e burette.
I matracci tarati vengono utilizzati per preparare e diluire soluzioni per un volume specifico. Sono contrassegnati con TC, che sta per "contenere".
Sono calibrati per contenere un volume accurato a temperature specificate, dove il coefficiente minimo di espansione del vetro consente un volume quasi costante nonostante piccole variazioni.
Le pipette etichettate TD erogano un volume specifico a una data temperatura. Sono calibrati per tenere conto del drenaggio del film sulle pareti di vetro, che varia con i tempi di consegna.
Le pipette volumetriche con taratura corretta erogano un singolo volume con precisione fino a quattro o cinque cifre significative. Le pipette di misura erogano volumi diversi con una precisione inferiore fino a tre cifre significative.
Una buretta è un tubo calibrato per contenere il titolante che può essere erogato con precisione tramite il sistema di valvole manuali per controllare il flusso del titolante.

taratura della vetreria

La taratura accurata della vetreria, come i matracci volumetrici, le pipette e le burette, è essenziale per garantire delle misurazioni accurate nel laboratorio analitico. La taratura aiuta a mantenere la coerenza tra le misurazioni e previene gli errori derivanti da volumi imprecisi. Ampolle volumetriche

I matracci volumetrici sono progettati per preparare soluzioni acquose di volumi precisi in modo accurato con una linea di taratura sul collo. Per calibrare un matraccio volumetrico, è importante riempirlo con acqua distillata fino a quando il menisco (la superficie curva del liquido) non si allinea con il segno di taratura. La visualizzazione del menisco a livello degli occhi garantisce letture accurate. La taratura viene in genere eseguita a una temperatura specifica (~20°C) per tenere conto dell'effetto della temperatura sul volume. Se il livello dell'acqua è sopra la linea, bisogna scolarla con attenzione fino a quando non tocca il segno; se la linea dell'acqua è sotto, va aggiunta altra acqua goccia a goccia fino a raggiungere il segno. Dopo la calibrazione, la capacità del matraccio può essere confermata pesando l'acqua e confrontandola con il valore teorico basato sulla sua densità.

Pipette

Le pipette vengono utilizzate per trasferire specifici volumi di liquido.

Pipette volumetriche: sono progettate per erogare un singolo volume altamente accurato, di solito a quattro o cinque cifre significative. Per la calibrazione, la pipetta viene prima pulita e risciacquata con la soluzione da misurare, riempita fino al segno di calibrazione e lasciata scolare completamente in un contenitore. La precisione viene quindi verificata pesando l'acqua erogata e confrontandola con il volume teorico basato sulla densità di quest’ultima.

Pipette graduate: a differenza delle pipette volumetriche, le pipette graduate sono contrassegnate con una serie di linee e possono erogare più volumi, ma con una precisione leggermente inferiore, generalmente fino a tre cifre significative. Anche il menisco dev’essere attentamente osservato durante la calibrazione e la misurazione.

Buretta

Una buretta è un lungo tubo di vetro graduato con un rubinetto a un'estremità che eroga con precisione quantità variabili di una soluzione, in particolare nelle titolazioni. Quando si calibra una buretta, bisogna assicurarsi che il menisco sia correttamente allineato con le marcature sia prima che dopo la titolazione, ed è importante controllare che il volume erogato sia quello previsto, confrontando il peso dell'acqua erogata con il suo valore teorico. Il serbatoio della buretta contiene delle marcature per indicare il volume del liquido. Il rubinetto, o rubinetto di arresto sul fondo, funge da valvola manuale che consente agli utenti di controllare il flusso del liquido dal serbatoio, consentendo una misurazione precisa della quantità erogata.

Altra vetreria

Altri tipi di vetreria da laboratorio, come i cilindri graduati, sono comunemente utilizzati anche per le misurazioni del volume, ma offrono una precisione inferiore rispetto alle apparecchiature volumetriche. Solitamente erogano volumi fino a tre cifre significative, adatti per i lavori meno precisi. Tuttavia, la calibrazione di questi articoli è comunque importante per mantenere l'affidabilità della misurazione.

La calibrazione della vetreria da laboratorio garantisce delle misurazioni accurate e affidabili, il che è fondamentale per mantenere l'integrità dei risultati analitici. Sia che si utilizzino dei matracci volumetrici, delle pipette, delle burette o altra vetreria, le tecniche di calibrazione appropriate aiutano a prevenire gli errori e a migliorare la precisione del lavoro di laboratorio.

Taratura della vetreria

La taratura accurata della vetreria, come i matracci volumetrici, le pipette e le burette, è essenziale per garantire misure accurate ...

Education

Didattica

JoVE Core

Analytical Chemistry

Chimica Analitica

Unit 1

Unità 1

Method Development and Sampling Techniques

Sviluppo del Metodo e Tecniche di Campionamento

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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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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Choosing Samples for Reliable Results

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sample-preparation-for-analysis-advanced-techniques

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Sample Transport and Storage Basics

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contaminants and errors

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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