All Interactive lab primer - lab techniques articles
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ResourceReflux with addition
A reactant is added to the refluxing reaction mixture in a controlled way via an addition funnel. This can be done to prevent exothermic reactions getting out of control. Video: Reflux with addition video
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ResourceThin layer chromatography
The technique of Thin Layer Chromatography (TLC) is normally used as an analytical method to follow the progress of a reaction, to analyse mixtures or to establish conditions for a preparative separation of compounds using column chromatography. The stationary phase (often silica) is coated on plastic or aluminium plates. The ...
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ResourceColumn chromatography
The separation of mixtures produced in chemical reactions is often carried out by passing the mixture through a stationary phase of silica held in a column. Solvents move compounds at different rates through the silica allowing them to be separated into fractions by collecting the emerging solvent. This can ...
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ResourceHeating under reflux
The term ‘reflux’ describes an arrangement in which a reaction is carried out in a boiling solvent with the vapour being condensed and returned to the reaction vessel. Refluxing is carried out when reactions need to be heated to give a reasonable yield of product in a reasonable time. ...
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ResourceDean-Stark apparatus
There are many equilibrium reactions that yield water as a co-product. It is the co-produced water that prevents a high yield of product being obtained. The removal of the water is necessary to drive the reaction to completion and this is done using Dean-Stark apparatus. The reaction is carried out ...
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ResourceSteam distillation
The extraction of a crude mixture containing water-insoluble material (such as natural products) can be achieved by co-distillation with steam. Video: Steam distillation video
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ResourceMelting point determination
The measurement of melting points is a relatively straightforward procedure that is carried out to determine the purity of a compound or to assist with its identification. A pure compound will melt over a relatively narrow temperature range, impurities both lower and widen the temperature range over which a compound ...
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ResourceDrying liquids
There are many instances when it is necessary to remove traces of water from a solution or liquid. One common example is the drying of an organic layer after a solvent extraction. The technique involves adding a suitable solid drying agent to the liquid followed by its removal by gravity ...
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ResourceCooling mixtures
Cooling baths are very useful in chemistry labs to control exotherimc reactions. In this resource we share various recipes for making cooling baths to temperatures below 0°C. There are many instances where you will need cooling as part of the procedure, for example in recrystallisation, carrying out reactions at low ...
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ResourceDistillation
Distillation separates liquids on the basis of them having different boiling points. Video: Distillation video
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ResourceSolvent extraction
This technique uses two solvents which are immiscible, for example an organic solvent such as diethyl ether can be used to extract an organic compound from an aqueous solution leaving water soluble impurities behind. A variation of this is acid - base extraction where acidic or basic compounds are extracted ...
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ResourceRecrystallisation
Recrystallisation is a means of purifying solids. If carried out correctly the final product will be both of a high yield as well as pure. Video: Recrystallisation video
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ResourceVacuum filtration
When a solid needs to be isolated from a solution it is normally done at a reduced pressure using a Buchner flask and Buchner funnel. Video: Vacuum filtration video
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ResourceStandard solution
A standard solution is a a solution of accurately known concentration prepared from a primary standard (a compound which is stable, of high purity, highly soluble in water and of a high molar mass to allow for accurate weighing) that is weighed accurately and made up to a fixed volume. ...
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ResourceSoxhlet extraction
When a compound of low solubility needs to be extracted from a solid mixture a Soxhlet extraction can be carried out. The technique places a specialised piece of glassware in-between a flask and a condenser. The refluxing solvent repeatedly washes the solid extracting the desired compound into the flask. ...
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ResourceWeighing compounds using a balance
Weighing is done to ensure the correct amount of a reactant is added to a reaction, for the preparation of standard solutions or the weighing of a product to calculate a yield. Video: Weighing compounds using a balance video
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ResourceFractional distillation
Fractional Distillation is used to separate compounds with boiling points that are close. Video: Fractional distillation video
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ResourceUsing a rotary evaporator
A rotary evaporator is used to remove large amounts of solvent from solutions at a reduced pressure. This is often done to isolate a product from a chromatographic separation or a solvent extraction. Video: Using a rotary evaporator video
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ResourceRunning an infrared spectrum
Infrared (IR) spectroscopy is a technique which reveals the bonds present in a compound and therefore can be used to identify functional groups. A sample of reaction product can be analysed to confirm its composition by comparison to a pure sample, or to judge the extent of reaction by comparison ...