All Practical skills and safety articles – Page 13

Resource
Heating 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. ...
Resource
Dean-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 ...
Resource
Steam 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
Resource
Melting 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 ...
Resource
Drying 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 ...
Resource
Titration

The addition of one reagent (the titrant) from a burette to another reagent until an end-point is reached is known as a titration. These have to be done with great care and precision to establish reliable and accurate results. Video: Titration video
Resource
Cooling 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 ...
Resource
Distillation

Distillation separates liquids on the basis of them having different boiling points. Video: Distillation video
Resource
Solvent extraction

2016-06-16T11:32:00Z

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 ...
Resource
Recrystallisation

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
Resource
Vacuum 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
Resource
Standard 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. ...
Resource
Soxhlet 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. ...
Resource
Mission starlight

The mission? To protect astronauts from the effects of harmful UV light
Resource
Weighing 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
Resource
Fractional distillation

Fractional Distillation is used to separate compounds with boiling points that are close. Video: Fractional distillation video
Resource
Using 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
Resource
Running 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 ...
Resource
Hot gravity filtration

This is the simplest kind of filtration when the solution to be filtered is poured through a filter paper in a filter funnel. The filtration of hot solutions through a funnel and fluted filter paper is often carried out as part of a recrystallisation. Gravity filtration is generally carried out ...
Resource
Volatile product distillation

A technique to remove a volatile product from a reaction mixture to prevent further reaction taking place. Video: Volatile product distillation video