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Laboratory equipment from A-Z


Evaporating Dish
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An evaporating dish, also known as a “porcelain dish“, is an open container used for heating solutions and liquids. Most evaporating dishes are made of porcelain or ceramics.
The particularly flat and semi-deep shape ensures that the heated liquid evaporates quickly.

To avoid confusion: An evaporating dish has a thinner wall than a mortar. Thus, it is allowed to be heated.

To heat liquids in the evaporating dish above a gas burner, use crucible tongs or place it on a tripod.


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A beaker is a cylindrical container with a flat bottom and a small spout for pouring. It is used in various ways and is therefore available in a wide range of sizes.

A beaker is used e.g. to collect and mix liquids. Likewise, it can be helpful when preparing solutions as the content can easily be stirred with a glass rod or a stirring bar due to the large opening.
Most beakers are made of borosilicate glass, which makes them resistant to heat and most chemicals.

Accordingly, the heating of a solution in a beaker with a gas burner (shown here with boiling stones on a tripod) is no>


Bubble Counter
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The bubble counter is used to monitor gas flow (for example in a distillation apparatus).
Usually it is filled with liquid paraffin, as this reagent is inert towards most gases. The high viscosity of the oil also helps to keep track of the bubbles.

The tubes are secured to the bubble counter with tube clips.
The inlet tube ist connected to the inlet pipe so that the gas has to stream through the bubble counter liquid.


Büchner Funnel
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The Büchner funnel is a porcelain laboratory instrument used for filtration under vacuum.
It is placed on top of a side-arm vacuum flask (Büchner flask).

A rubber gasket (Büchner ring) is placed on the funnel which is then positioned on the vacuum flask.

The side-arm flask is connected to a vacuum pump with a rubber tube. The rubber tube should not be fixed with a clamp.

Before starting the filtration, a suitable round filter paper is placed on top of the porous plate inside the funnel.
The filter needs to…

  • fit the funnel (it can be cut to size if necessary)
  • lie flat and cover all the pores

The filter paper is moistened with the solvent, in this case water.

Filtration of a suspension
The vacuum tap is opened so that the filter paper is sucked in. Subsequently, the suspension is added. The formed filter cake additionally has a filtering effect.

To clean the filter cake, the rubber tube is removed (keeping the pump running) and the washing solution is poured onto the filter cake. By applying vacuum again, the washing solution is sucked into the vacuum flask.

The filter cake is put on a watch glass or petri dish and the moist filter paper removed with tweezers.
The filter cake is further processed, e.g. by drying it.


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A burette is used for a titration. With the help of the burette an exact amount of analytical solution can be added to a sample solution. The dose can be adjusted by turning the valve.
The burette must always be clamped vertically, ideally with the help of a burette holder.

In order to fill a burette with the analytical solution, the valve must first be closed.
It must be made sure that there are no bubbles in the burette.
The burette is filled with the help of a funnel until the analytical solution is above the scale. Subsequently, the analytical solution is released by opening the valve until the level reaches the scale value „0“ (zero).

It is decisive to accurately read off the volume of the analytical solution during the titration.
To help with this, a colored stripe (Schellbach stripe) is situated at the back of the burette.
Through light refraction there is a constriction of the Schellbach stripe at the lower end of the meniscus and two peaks become visible in whose center the level of the analytical solution is read off.

Furthermore, it is important to make sure that one‘s eye level is on the height of the fluid level when reading it off to guarantee a horizontal and correct read.
If the analytical solution is not clear and the constriction of the Shellbach stripe not visible, the volume is read off at the highest point of the liquid meniscus.


Burette Clamp
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The burette clamp is an aid to secure a burette.
It makes sure that the burette is always clamped vertically.
The burette clamp is attached to a lab stand.

The burette clamp is opened using index finger and thumb.
The burette is secured by positioning it between the rubber rollers.
Subsequently, the clamp is carefully closed and the burette is ready for use.

Left: A complete apparatus with burette and burette clamp.
Right: Should no burette clamp be available in the lab, the burette can carefully be secured using a support clamp as shown here.


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The distiller is used to condense the product of a distillation. It consists of a Claisen flask, a Liebig condenser and a vacuum inlet.

The Claisen flask serves as a connection between the sample vessel and the Liebig cooler.
As shown here, the Claisen flask is secured at the ground glass joints with clamps.

If the temperature needs to be checked during distillation, a thermometer is connected to the Claisen flask. The temperature sensor of the thermometer needs to be located under the entrance of the Liebig condenser.

The thermometer can be attached to the distiller via a quick-fit or ground joint.
Both options can also be used during vacuum distillations.

The Liebig condenser is needed to cool the gas for condensation. The cooling liquid (usually water) ist connected to the condenser according to the countercurrent exchange mechanism.

The vacuum adapter is located at the end of the Liebig condenser.
In vacuum distillation, a vacuum pump is connected to the vacuum adapter by means of a vacuum hose.
A round-bottomed flask or a destillation spider with flasks can be used to collect the distillate. By using a distillation spider, different fractions can be collected without having to ventilate the apparatus during a vacuum distillation.


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The tripod is used when working with a gas burner.

To place an evaporating dish on top of the tripod a wire gauze is needed.

The evaporating dish is placed in the center of the wire gauze.

When using a crucible the wire gauze is replaced by a clay triangle. The crucible is placed tightly in the triangle.

When placing the burner under the tripod, make sure that it can be moved easily if necessary.


Erlenmeyer Flask
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An Erlenmeyer flask is a conical glass vessel.
It is particularly useful when the contents of the flask have to be swirled (e.g. during a titration), as the risk of spillage can be minimized due to the special design.

During a titration, the solution in the Erlenmeyer flask is swirled so that the solutions mix well.
The conical shape prevents the solution from splashing out.

The Erlenmeyer flask is also used for reactions with gas evolution.
The gas produced can be discharged via a glass tube (gas discharge tube).

Furthermore, Erlenmeyer flasks with ground-glass joints exist which can be closed with a stopper.

The stopper can be secured with a clip from metal or plastic.


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The desiccator is used to dry products or protect hygroscopic chemicals from humidity. The desiccator is made of heavy glass, which allows to apply vacuum.
The use of a desiccant supports the drying process. Common desiccants are calcium chloride, silica gel or phsphorus pentoxide.

The desiccant is stored in the reservoir below the sievelike platform.

The sample is stored on a watch glass or petri dish, sealed with punctured aluminum foil and placed on the platform.
In order to prevent damage the lid should be carefully slid on and off the base. To maintain a good seal, vacuum grease needs to be applied to the flanges.

To evacuate the desiccator a hose of a vacuum pump is applied to the stopcock. The hose does not need to be fixed with a clamp. The stop cock is opened.

After applying the vacuum the Stopcock is closed and the hose can be disconnected.

To take out the dried sample, the desiccator needs to be vented very carefully. The stopcock is to be opened slowly.


Filter Paper
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Filter paper is used for material separation or paper chromatography.
Commonly, paper filters with a pore size of 4-7 µm are used for medium-fine precipitates (quality 3 hw).

If the residue is of interest during preparative work, a filter paper disk in a suction funnel is used as that way the filter cake can easily be removed.
Too large filters can easily be cut out to the right size.

If the filtrate is of interest during preparative work, a folded filter is used.
It is placed in a glass funnel.
The large filter area allows for a faster filtration.

If no folded filter is available, a filter paper disk can be folded following the displayed procedure.
In the final step (6), the folded filter is turned inside out and can then be used.

Special filters are used for analytical work. They have a defined ash content and are incinerated with the residue. The ash content is stated on the packaging.
The pore size of special filters is smaller than that of preparative filter papers. They are commonly used in combination with fast filtration funnels and require a specific folding technique.

One important aspect to correctly use an analytical funnel is to correctly fold the filter. In step 1 the filter is folded in the middle.
In step 2 the filter is folded at an angle so that the bottom layer slightly sticks out (step 3).
In order for the filter to sit closely, the top groove is torn twice in step 4. This way there is a softer transition between the two layers.


Filter Crucible
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A filter crucible is used under vacuum for analytical filtrations.
Filter crucibles have fritted glass filters of various pore sizes.
With pore sizes below 2 μm, finer residues can be filtered than when using a porcelain suction funnel (filter paper).

The following components are required to filter with fritted glass: rubber gaskets, a crucible adapter and a filter flask.

The rubber gasket is placed on the filter flask.
The crucible adapter is positioned in the rubber gasket.

The second rubber gasket is placed on the crucible adapter as shown in the picture.

Finally, the filter crucible is placed in the rubber gasket.

When the filter crucible is in place, its bottom edge should protrude the rubber gasket. Only then, the filtrate will not come in contact with the rubber gasket.

The suction flask can now be connected to the vacuum and filtration can begin.


Filter Rack
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A filter rack is a used for funnels during filtration. They make sure that the funnels are always positioned vertically.
The glass funnel is placed in the rack and and an appropriate connection vessel is positioned underneath.

The funnel tube should always protrude the beaker edge but may not be immersed in the filtrate.

As the assembled filter rack takes up a lot of space, it is typically found in its components in the lab.


Gas Burner
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A gas burner, also known as a Bunsen burner, is used to heat and burn chemicals.

Before use, a gas tube is connected to the gas supply and the gas burner.
The tube is secured with tube clips.
The function of gas burner is adjusted via the air supple and the throttle valve.

Before igniting the Bunsen burner, the throttle valve is closed and the air supply shut off.
Subsequently, the gas valve is opened and the fire source is held over the chimney.
By opening the throttle valve, the burner is ignited.

By adjusting the air supply, the flame temperature can be tuned.
A distinction is made between a glowing flame (left) and a whooshing flame (right).

To extinguish the flame, first the air supply is shut off, then the throttle valve and finally the gas valve is closed.
The flame is left to burn out.
Subsequently, the air supply is reopened to prevent the thread from jamming during cool down.


Gas Washing Bottle
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A gas washing bottle is used to physically or chemically purify gases.
It is either filled with a suitable absorbent (chemical purification) or left empty (physical purification).

When using an absorbent (chemical purification) the correct flow direction of the gas is important.
The gas is always directed into the absorbent through the inlet pipe (red arrows).

To prevent backflow of the absorbent, an empty gas washing bottle (physical purification) is connected between the apparatus and the filled gas washing bottle.
The safety bottle is always connected inversely.


Stopcock Key
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A stopcock key is a slightly conically tapered plug for stopcocks. The stopcock key must be secured with a washer, an O-ring and a screw-cap.
Stopcock keys are available in different sizes and a distinction is made between glass and teflon plugs.

Glass stopcock keys may only be used in ground-glass stopcocks and require the use of grease.
If the stopcock key is horizontal, the stopcock is closed. If it is vertical, the stopcock is open.
Stopcock keys from teflon may only be used in smooth stopcocks and shouldn‘t be greased.


Stirring Hot Plate
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A stirring hot plate is a magnetic stirrer with a heating function.
Solutions in reaction vessels and/or heating baths can be stirred and simultaneously heated.

The stirring speed is adjusted with the right control knob.
The temperature can roughly be adjusted with the left controller.

To accurately adjust the temperature of the heating bath, a contact thermometer is connected.
The temperature sensor must be immersed in the heating bath but not touch to bottom.

The contact thermometer is connected at the back of the stirring hot plate as shown in the picture.

If the stirring hot plate is used without a contact thermometer, the the temperature connector (left) must be covered with the cap, as otherwise the heating function does not work.
The temperature can then roughly be adjusted using the controller.

Stirring bars are used to continuously mix the reaction solution in a flask (see picture) or the heating bath.

They are available in different shapes and sizes.


Cooling Bath
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A cooling bath is used to cool down reactions or to decrease solubility, e.g. during recrystallization.
To maintain the low temperature, the sample is placed in the cooling bath so that it is fully surrounded by the cooling agent. Please note, the sample flask should be secured with a support clamp.

Depending on the desired temperature, cooling baths can be prepared in the lab.
A glass bowl is used as container.

If 0°C are desired, an equal mixture of ice and water is prepared.

For temperatures around -20°C a mixture of 1/3 sodium chloride (NaCl) and 2/3 ice is prepared.
This cooling bath must be mixed thoroughly.


Round-bottomed Flask
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A round-bottomed flask is standard reaction vessel made of glass, which consists of a lower spherical vessel and a cylindrical neck (socket, standard size: 29 mm or 14.5 mm).
Round-bottomed flasks are available in many different sizes (e.g. 50 mL, 100 mL etc.) and must always be kept on a cork ring due to their shape.

Furthermore, there are round-bottomed flasks with two or three necks.

In contrast to Florence flasks (flat bottom), round-bottomed flasks with ground-glass joints can be put under vacuum.
Round-bottomed flasks are ALWAYS secured at the joint with support clamps.
Additionally, all round-bottomed flasks can be heated. The use of a stirring bar ensures ideal mixing of the reaction solution.


Gas Syringe
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A gas syringe is used when handling gases (insert or withdraw) or to measure the volume of evolved gas.
The plunger can move freely in the syringe when the valve is open.
To ensure this, it is important that the plunger is not damaged during transport.

The tip of the syringe is connected to the apparatus via gas tubing or pierced stoppers.
When the valve is open, gases can enter the syringe.

The volume of gas in the syringe can be determined via the mark on the plunger.


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A cuvette is a sample vial for spectroscopic applications, made mostly of plastic or quartz glass.
In photometry, a cuvette of 1 cm diameter is used.
The cuvette should only be touched at the rough surfaces, as fingerprints on the smooth surfaces can interfere with the measurement.

The cuvette is filled with a solution and subsequently placed in the spectrometer.


Conductivity Meter
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A conductivity meter (conductometer) is used to determine the conductivity of a solution.
It has a cap to protect the delicate electrode from impact.
The electrical conductance G is a measure for the amount of dissolved and dissociated substance.
It is inverse proportional to the ohmic resistance R of the solution and is reported in siemens [S].

The resistance R of the conducting electrolyte solution is dependent on the resistivity ρ (unit: siemens per meter [S/m]) and the cell constant Z.

The cell constant Z results from the distance s between the electrodes and the area of the electrodes A.

The value of the cell constant is provided by the manufacturer of the measuring cell or has to be determined by calibration.

In the practical courses, the conductivity G is mostly determined as the ratio of the measured current I and the applied high-frequency alternating voltage U.
The resistivity and thus also the measured conductivity is dependent on:

  • the concentration of the dissolved substance and its degree of dissociation.
  • the valency and movility of the dissolved particles.
  • the temperature of the solvent.

First, the power supply is connected to the conductivity meter.
The multimeter is connected to measure the current intensity.

A second multimeter is connected in parallel to measure the voltage.

The conductivity meter is immersed vertically into the solution and the measured value is noted down.
Subsequently, the conductivity meter is rinsed with purified water.


Magnesia Bridge
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A magnesia bridge is used to prepare small amounts of molten mass.
It is made of magnesium oxide and can be heated up to 2600°C.

The sample is placed on the magnesia bridge and held into the flame of a bunsen burner with crucible tongs.
It must be made sure that the molten mass does not drip off the magnesia bridge.


Magnesia Rods
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Magnesia rods are heat-resistant white rods of 10-15 cm length.
They consist of pressed magnesium oxide and have a melting point of ca. 2800 °C.

Magnesia rods are used e.g. for flame tests in qualitative analyses.
The rod is initially annealed with a bunsen burner and then immersed in the sample so that some of it sticks.
It is subsequently held in the flame again and the flame color is observed.
green: copper salt
red: potassium salt


Volumetric Flask
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A volumetric flask is a flat-bottomed flask with a calibration mark.
Only the nominal volume can be measured with a volumetric flask.
Volumetric flasks are always calibrated for inlet (In).

The imprint of a volumetric flask gives the following information:
500 ml corresponds to the nominal volume until the calibration mark, ± 0.25 is the systematic tolerance, 20 °C is the calibration temperature, In means calibration for inlet.

The volumetric flask contains its exact nominal volume when the bottom edge of the meniscus is at the calibration mark.


Graduated Pipette
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A graduated pipette is used to accurately dose liquids.
In contrast to a volumetric pipette, variable volumes can be measured with a graduated pipette.
However, this happens at the expense of the accuracy.

Typically, all volumetric instruments are provided with details regarding accuracy and application.
The following information is given on the imprint of a graduated pipette:
10 ml corresponds to the nominal volume , "Ex" means calibration for discharge, 20 °C is the calibration temperature and ± 0.06 corresponds to the tolerance.

Pipettes must always be held vertically.
Only this can guarantee an exact reading of the volume and prevent solution from advancing into the pipette aid.

When using a pipette, the solution is taken up until the 0 (zero) mark (lower edge of the meniscus).

The measured volume results from the difference after liquid release.
If the total nominal volume is needed, it must be made sure that a small residue is left in the pipette tip.
This residue has already been taken into account during the calibration.


Graduated Cylinder
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A graduated cylinder is used to roughly measure liquids.
Please note, due to their high center of mass graduated cylinders are easily tipped over!

Typically, all volumetric instruments are provided with details regarding accuracy and application.
The imprint of a graduated cylinder gives the following information:
50 = nominal volume
1 = scaling
ln = calibrated for inlet
20 °C = calibration temperature
± 0.75 mL = tolerance

The measured value is read off at the level of the phase boundary (below the meniscus if there is one).
The volume here is:
38 ml (± 0.75 mL).


Pasteur Pipette
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Pasteur pipettes are used to transfer small volumes of liquid.
They are typically tapered small glass tubes and hold a volume of 2 mL.
The liquid is sucked up and released (also dropwise) with the help of a suction cup.

Pipettes must always be held vertically and the solution only transfered short distances.

If not held vertically, the solution could move into the suction cup and contaminate it.


Pipette Filler
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A pipette filler is a rubber bulb used to fill glass pipettes.
A = valve to release air
S = valve to absorb liquid
E = valve to empty pipette

The top of the pipette is inserted in the bottom of the rubber bulb.

Valve A is opened by squeezing. Air can be released from the pipette filler by simultaneously squeezing valve A and the bulb.

In order to take up liquid into the pipette, valve S is opened by squeezing.

The pipette is emptied by opening (squeezing) valve E.

After use, the pipette filler should be removed from the pipette. Then, it is ventilated by pressing valve A.


pH Meter
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By means of a pH meter, the pH value of a solution is determined and displayed.
pH meters come in different models (see picture).

  • pH meter with a combination electrode (left)
  • Pocket pH meter (right)

In the practical course, glass electrodes are used as measuring cells.
To prevent damage, the measuring cell must be handled carefully (NO stirring).
When not in use, the measuring cell of the pH meter is stored in a 3 m KCl solution. It may not dry up as the diaphragm of the measuring cell has to be kept at neutral potential and and conductive.

Before use, the pH meter must be calibrated.
For the calibration, buffer solutions of known pH value are used.

  • pH=4 / pH=7 (low pH value)
  • pH=7 / pH=9 (high pH value)

If a low pH value is expected for the sample, the pH meter is calibrated with buffer solutions of pH = 4 / pH = 7.
By contrast, if high pH values should be measured, the calibration is done with buffer solutions of pH = 7 / pH = 9.
After the measurement, the mesuring cell is rinsed with purified water.

Calibration of the pH meter:
Example for a low pH value (pH < 7)

  • Measurement of buffer pH = 4
  • Adjustment of the value at the pH meter with the wheel
  • Cleaning of the measuring cell with purified water
  • Measurement of buffer pH = 7
  • Adjustment of the value at the pH meter with the wheel
  • Cleaning of the measuring cell with purified water
  • Repetition of steps 1-3

For pH measurements of acidic solutions (pH<7) the following order should be followed:
pH = 4 / pH = 7 / pH = 4
For pH measurements of basic solutions (pH>7):
pH = 9 / pH =7 / pH = 9
After calibration of the measuring cell it should be stored in a KCl solution.

For the measurement of the pH value, the calibrated measuring cell is immersed in the sample solution and the value is read off.
After the measurement, the measuring cell is rinsed with purified water and placed in the storage solution (KCl solution).


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A quick-fit is a ground joint with a screw adapter. With the help of a quick-fit, thermometers and glass tubes can be connected to ground-glass equipment.

A quick-fit consists of:

  • a screw cap
  • a rubber gasket
  • a PTFE-disk
  • a glass adapter

First, the PTFE disk is slid on, which is resistent to chemicals.
That way the following rubber gasket is protected.
The screw cap is attached last.

The screw cap with rubber gasket and PTFE-disk is slid on the thermometer.
The height of the thermometer can be adjusted.

The glass adapter is secured with a clip and the thermometer with screw cap is screwed on the quick-fit.
If needed, the height of the thermometer can be adjusted.


Test Tube
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Test tubes are small glass containers with an opening at one end. They are used for simple chemical reactions, investigations and to preserve small amounts of liquid. They can vary greatly in length and size, but the standard test tubes are 16 cm long and have a diameter of 16 mm.
For better handling, test tubes are placed in a rack made of wood, plastic or coated wire.

For safe handling in the lab, test tube holders (typically from wood) are used.

With the help of the test tube holder, a test tube can be heated over a Bunsen burner. To prevent boiling delay, the heating should be interrupted regularly. The opening of the test tube should always held towards the fume hood and away from the body.

Furthermore, the test tube holder should not come in contact with the flame.


Mortar and Pestle
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To avoid confusion: A mortar has a thicker wall than an evaporating dish.
Thus, it is not allowed to be heated.

A mortar is used to grind or rub solids.
The pestle may only be used to rub and not to pound.


Reflux Condenser
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The reflux condenser is used to recover solvent.
In contrast to a Liebig condenser, a reflux condenser is not used for substance separation, but it prevents solvent loss during a reaction.

The choice of the reflux condenser (jacketed coil condenser, Allihn condenser or coil condenser) depends on the boiling point of the solvent and the temperature of the coolant.

A coil condenser has a cooling coil.
It is used as a standard in the lab.

An Allign condenser has a cooling jacket.
It is also used as a standard in the lab.

Jacketed coil condensers are used for special applications at very low boiling points.
They have both a cooling jacket and a cooling coil.

Reflux condenser are secured with a support clamp at the top ground-glass joint.

If the reaction mixture has to be protected from moisture, a filled drying tube is placed on the reflux condenser and secured with a clip.

The cooling water is connected so that the entire cooling area is filled with water.
Depending on the required cooling temperature, water or a water-glycol mixture is used for cooling.


Lab Tubing
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Lab tubes are used to direct gasses and liquids.
Depending on the area of application, different tubing (material and size) is chosen.

A vacuum tube is used as the connection between the inhouse vacuum or a vacuum pump and the experimental apparatus.
Vacuum tubes are typically not secured.
Due to its thick walls, the tube maintains ist shape under vacuum.
The inhouse vacuum connections are indicated by a black dot on the valve.

Rubber tubes can be used e.g. as the connection between the gas valve and the gas burner.
It is important to secure the rubber tubing with tube clips.
The natural gas valves in the lab are yellow.

PVC tubing is used to transfer gas or liquids as well as in the cooling water circuit.
The rigid, transparent tubes are secured by tube clips.
They are resistant toward most chemicals.

Textile tubing is used for equipment where an overpressure is formed.
The fabric fibers ensure that the tube can resist higher pressure.
With this reinforcement, textile tubes can also be used under vacuum, e.g. in Schlenk apparatuses.
They must always be secured with tube clips.


Fast Filtration Funnel
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A fast filtration funnel, also known as an analytical funnel, is used to filter small amounts of residue.
It is made of glass and has an indentation in the funnel cone.

The funnel ist placed in a filter rack and a collection vessel is positioned underneath.

Filter paper disks are used in fast filtration funnels.
The filter paper is properly folded and dampened, thereby forming a cavity between the bottom part of the filter cone and the filter paper.
When filling the funnel with solution, a water column is formed.
The suction of this water column is responsible for the fast filtration speed.

After the preparation of the funnel, the sample is poured in the filtration cone.
It should be made sure that the sample does not pass the rim of the filter paper.

When filtering, the funnel tube should touch the wall of the beaker to ensure a continous flow.

The funnel tube should not be immersed in the solution as then the filtration could come to a halt through the build-up of counterpressure.


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A septum is an air-tight seal that enables the removal or addition of substances with the help of a syringe and canula.

To seal a flask, the septum is first placed on the flask (left) and then flipped over the ground-glass joint (right).

Using a canula, the septum can be pierced and substance removed.
When doing this, it is important use a second canula for pressure equalization.


Lab Bottle
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A lab bottle is used to store aqueous solutions.
It is available in different colors and sizes and has a ground-glass joint at the neck of the bottle.

Accordingly, the lab bottle can be sealed tightly with a ground-glass stopper.

A lab bottle must be labeled with a permanent marker so that it is unambiguously clear what the content is.
Beyond the substance itself, all H and P phrases as well as hazard symbols should be noted on the lab bottle.


Support Stand
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The support stand consists of a support rod and base.
With the help of a clamp holder, support clamps can be attached to the rod.

Initially, the support clamp is closed.
It can be opened by turning the adjusting screw and a flask can be clamped.


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Stoppers are used to cap laboratory equipment.
As needed, glass, plastic or rubber stoppers can be used.

Ground-glass stoppers are used to cap glass apparatuses with ground-glass joints and should be secured with a joint clip.

Plastic stoppers are used to cap glass equipment.
They can also be used to seal extraction vessels.

Rubber stoppers can be pierced and used e.g. to secure glass tubes.
Furthermore, they can be used to cap test-tubes.


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There are various versions: analog and digital as well as high- and low-temperature thermometers.
Analog thermometers are filled with metal alloys or special liquids (e.g. alcohols).

Thermometers are expensive precision instruments that should always be treated with care!
Thermometers are not glass rods and should not be used to stir solutions.
The choice of thermometer depends on the expected temperature range and the sample.
The wrong choice could lead to damage.

An analog thermometer is secured by a support clamp so that it is immersed in the solution without touching the bottom.
Analog thermometers have rather small measuring ranges, e.g.:
-200°C to +30°C, -100°C to 200°C, -50°C to 300°C

Digital thermometers typically have larger measuring ranges (e.g. -200°C to +400°C).
As the sensors are made of metal, they are labile towards acids or bases.

Analog thermometers are commonly used in airtight glass apparatuses. With the help of a „quick-fit“ they are connected to the apparatus.

In evacuated apparatuses ground joint thermometers should be used for the sake of tightness.


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A crucible is typically a fireproof, inert container used to heat up and dry substances or prepare molten mass.
The material and shape of the crucible depends on its application.

A crucible can be positioned optimally above a gas burner with the help of a clay triangle.
Porcelain crucibles must be heated up and cooled down slowly to prevent possible stress cracks.

A crucible in boat form is used for chemicals that are placed in a tubular furnace or a reaction tube.


Crucible Tongs
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Crucible tongs are mainly used to grip and hold crucibles.
The special oval shape of the gripping parts enables the crucible to be gripped and held securely.

With the crucible tongs, the crucible can be placed into the clay triangle.
In addition, the crucible tongs can also be used to hold other objects (e.g. metals during annealing).


Drying Tube
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A drying tube is used to protect material in an apparatus or a flask from humidity and simultaneously ensure pressure equalization.

The sphere of the drying tube is plugged with some glass wool to prevent the drying agent from entering into the apparatus.

Subsequently, the sphere is filled with a drying agent (e.g. CaCl2) and closed up with glass wool.

Die drying tube is then connected to the apparatus by the ground joint and secured with a clamp.


Dropping Funnel
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A dropping funnel is used to drop a solution into a reaction flask in equal portions and in a relatively defined time window.
Most dropping funnels have ground glass joints so that they can be attached airtight to the apparatus.
Accordingly, typically dropping funnels with pressure equalization are used.

The dropping funnel is secured with a support clamp at the top ground glass joint and connected to the apparatus.

After attaching the joint clamp, the valve is closed and the dropping funnel filled. Subsequently the dropping funnel is closed with a stopper.

The addition can be adjusted via the valve.


Watch Glass
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A watch glass is a curved plate of transparent glass. Its diameter can vary from 6 to 20 cm.

Watch glasses are used e.g. to weigh in small amounts of substances.

Additionally, solid material can be dried on watch glasses in drying cabinets or dessicators.

Furthermore, beakers or Petri dishes can be covered with a watch glass (instead of using a designated lid) to prevent contamination.


Volumetric Pipette
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Using a volumetric pipette, a defined volume can accurately be measured. For a given pipette, there is just one mark for this defined volume.

Typically, all volumetric measuring instruments are provided with details regarding accuracy and application.
The following information is given on the imprint of a volumetric pipette:
25 mL = nominal volume
Ex = calibrated for discharge
20 °C = calibration temperature
± 0.04 mL = tolerance
Pipettes must always be held vertically.
Only this can guarantee an exact reading of the volume and prevent solution from advancing into the pipette aid.

When using a pipette, the solution is taken up until the 0 (zero) mark (lower edge of the meniscus).

If the total nominal volume is needed, it must be made sure that a small residue is left in the pipette tip.
This residue has already been taken into account during the calibration.


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In the lab,chemicals are weighed in using different balances.
If a high accuracy is not necessary(like during preparative work), a laboratory balance is used (top picture). Accuracy: ±0.1 g

If a high accuracy is necessary(like during analytical work), an analytical balance is used (bottom picture). Accuracy: ±0.0001 g

Laboratory and analytical balances are expensive precision instruments that should always be treated appropriately and with care!
Contaminations should be prevented or directly removed.
Frequently switching laboratory and analytical balances on and off should be avoided.
Laboratory Balance

A sample container (e.g. a watch glass)is placed on the weighing plate.
To prevent the sample container from being weighed,the balance is tared(TARA).

The desired amount of the substance is weighed out and the displayed value is noted down.
The sample container is removed from the weighing plate and the balance is tared. If necessary, the surface is cleaned with a paper towel.
Analytical Balance

Before use,the balance must be tared to 0 with closed side windows.
After opening the side window, a sample container (here: watch glass) is placed on the weighing plate.
The side window is closed and after some time the weight of the sample container can be noted down.
The sample container is removed and a substance is added to it.
Subsequently, the sample container with the substance is placed on the weighing plate.
Once again the side window is closed and after some time the weight is noted down.
Finally,the difference between the two values is calculated to determine the exact weight of the sample.
Woulffsche Flasche-übersicht

Woulff Bottle
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A Woulff bottle serves as a safety device for vacuum pumps.
It is vacuum-tight and is interposed beween the apparatus and the pump when evacuating glass apparatuses.
This prevents chemicals from being drawn into the vacuum pump.
The two outer openings are connected to the apparature and the pump. The tubes should always be secured with tube clips.
The valve in the middle is used for ventilation.

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A centrifuge tube is a pointy container made from glass (top) or plastic(bottom). An advantage of plastic centrifuge tubes(e.g Eppendorf-Cap©)is that they can be closed with caps.

Centrifuge tubes are used in centrifuges. A centrifuge can separate the components of a suspension or emulsion through circular motion by which the solid ends up at the bottom of the centrifuge tube.