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

Dokładne pomiary objętości mają kluczowe znaczenie dla analiz opartych na rozwiązaniach. Standardowe wyposażenie wolumetryczne obejmuje kolby, pipety i biurety.
Kolby miarowe służą do przygotowywania i rozcieńczania roztworów dla określonej objętości. Są one oznaczone jako TC, co oznacza "zawierać".
Są one skalibrowane tak, aby zawierały dokładną objętość w określonych temperaturach, gdzie minimalny współczynnik rozszerzalności szkła pozwala na prawie stałą objętość pomimo niewielkich zmian.
Pipety oznaczone jako TD dostarczają określoną objętość w danej temperaturze. Są one skalibrowane tak, aby uwzględniać drenaż folii na szklanych ścianach, który różni się w zależności od czasu dostawy.
Pipety miarowe z odpowiednią kalibracją dostarczają pojedynczą objętość z dokładnością do czterech lub pięciu cyfr znaczących. Pipety pomiarowe dostarczają różne objętości z mniejszą dokładnością do trzech cyfr znaczących.
Biureta to skalibrowana rurka do przechowywania titranta, która może być precyzyjnie dozowana za pomocą ręcznego systemu zaworów w celu kontrolowania przepływu titranta.

kalibracja szkła miarowego

Dokładna kalibracja szkła miarowego, takiego jak kolby miarowe, pipety i biurety, jest niezbędna do zapewnienia dokładnych pomiarów w laboratorium analitycznym. Kalibracja pomaga zachować spójność pomiarów i zapobiega błędom wynikającym z niedokładnych objętości. Kolby miarowe

Kolby miarowe są przeznaczone do przygotowywania roztworów wodnych o dokładnych objętościach z linią kalibracyjną na szyjce. Aby skalibrować kolbę miarową, ważne jest, aby napełnić ją wodą destylowaną, aż menisk (zakrzywiona powierzchnia cieczy) wyrówna się ze znakiem kalibracji. Oglądanie menisku na wysokości oczu zapewnia dokładne odczyty. Kalibrację zazwyczaj wykonuje się w określonej temperaturze (~20°C), aby uwzględnić wpływ temperatury na objętość. Jeśli poziom wody jest powyżej linii, ostrożnie ją opróżnij, aż osiągnie znak; jeśli linia wody jest poniżej, dodawaj więcej wody kroplami, aż osiągnie znak. Po kalibracji pojemność kolby można potwierdzić, ważąc wodę i porównując ją z wartością teoretyczną opartą na jej gęstości.

 Pipety

Pipety służą do przenoszenia określonych objętości cieczy.

Pipety objętościowe: Są one zaprojektowane tak, aby dostarczać pojedynczą, bardzo dokładną objętość, zwykle do czterech lub pięciu cyfr znaczących. W celu kalibracji pipetę najpierw czyści się i płucze mierzonym roztworem, napełnia do znaku kalibracji i pozwala się jej całkowicie spuścić do pojemnika. Następnie dokładność sprawdza się, ważąc dostarczoną wodę i porównując ją z objętością teoretyczną opartą na gęstości wody.

Pipety miarowe: W przeciwieństwie do pipet miarowych, pipety miarowe są oznaczone serią linii i mogą dostarczać wiele objętości, ale z nieco niższą dokładnością — zazwyczaj do trzech cyfr znaczących. Menisk musi być również uważnie obserwowany podczas kalibracji i pomiaru.

Biureta

Biureta to długa, skalowana szklana rurka z kranem na jednym końcu, która dokładnie dozuje zmienne ilości roztworu, szczególnie podczas miareczkowania. Podczas kalibracji biurety upewnij się, że menisk jest prawidłowo wyrównany z oznaczeniami przed i po miareczkowaniu, i sprawdź, czy dozowana objętość jest zgodna z oczekiwaniami, porównując wagę dostarczonej wody z jej wartością teoretyczną. Zbiornik biurety zawiera oznaczenia wskazujące objętość cieczy. Zawór odcinający lub kran na dole służy jako zawór ręczny, który pozwala użytkownikom kontrolować przepływ cieczy ze zbiornika, umożliwiając dokładny pomiar dozowanej ilości.

Inne szkło

Inne rodzaje szkła laboratoryjnego, takie jak cylindry miarowe, są również powszechnie używane do pomiarów objętości, ale oferują niższą dokładność niż sprzęt objętościowy. Zazwyczaj dostarczają objętości do trzech cyfr znaczących, co jest odpowiednie do mniej precyzyjnej pracy. Jednak kalibracja tych przedmiotów jest nadal ważna dla utrzymania niezawodności pomiaru.

Kalibracja szkła laboratoryjnego zapewnia dokładne i niezawodne pomiary, co jest kluczowe dla zachowania integralności wyników analitycznych. Niezależnie od tego, czy używasz kolb miarowych, pipet, biuret czy innego szkła, właściwe techniki kalibracji pomagają zapobiegać błędom i poprawiają precyzję pracy laboratoryjnej.

Kalibracja szkła miarowego

Dokładna kalibracja naczyń szklanych, takich jak kolby miarowe, pipety i biurety, jest niezbędna do zapewnienia dokładnych pomiarów w ...

Education

JoVE Core

Analytical Chemistry

Chemia analityczna

Unit 1

Jednostka 1

Method Development and Sampling Techniques

Opracowywanie metod i techniki pobierania próbek

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

KLUCZOWE POJĘCIA I KONCEPCJE

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

development of analytical methods

Analytical Methods: Technique to Protocol

Analytical methods follow a clear path from technique to protocol. In analytical chemistry, a technique is the scientific principle used to explain a chemical measurement. A method applies that technique to a sample of interest. The next steps are procedure and protocol. A procedure gives the directions for carrying out the analysis with an analytical method. A protocol is the detailed set of guidelines for that procedure, and it should be followed closely to get the desired results. <br...

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Quality Control Charts and Lab Records

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Quality Checks in Analytical Testing

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qualitative analysis

Classical and Instrumental Sample ID

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Measuring Analyte Concentration

Quantitative analysis measures the amount of a specific substance, called the analyte, in a sample. If the sample composition is unknown, qualitative analysis comes first. That step identifies the components so the correct substances can be measured during the quantitative phase. This method depends on two key measurements. Scientists measure the sample quantity and also a property that is proportional to the amount of analyte. Together, these measurements help determine the analyte...

instrument calibration

Calibrating Lab Instruments for Accurate Results

Calibration helps lab instruments produce accurate and consistent results. It is important in manufacturing, healthcare, testing laboratories, and scientific research. Each instrument needs a calibration process that matches its design and function. This process improves data accuracy and helps results stay reliable. An analytical balance measures mass and needs regular calibration to stay precise. It is calibrated by comparing its readings with known standard weights. These weights act as...

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...

blank solutions

Blank Solutions in Analytical Testing

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sample preparation for analysis: overview

Preparing Samples by State and Form

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sample handling

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

analytical chemistry

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Calibrating Lab Glassware for Accurate Volume

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