![]() The colour can be used to identify the metal or its compounds (eg sodium vapour in a street lamp). Certain bright lines in these spectra cause the characteristic flame colour. When the electrons fall back to lower energy levels, they emit light of various specific wavelengths (the atomic emission spectrum). The electrons in the metal ions are excited to higher energy levels by the heat. calcium – orange-red (probably the least spectacular).potassium – purple-pink, traditionally referred to as ‘lilac’ (often contaminated with small amounts of sodium).sodium – yellow-orange (typical ‘street lamp’ yellow).A better way to produce a steady source of light is to use discharge tubes from the Physics Department – with a suitable risk assessment.) Teaching notes The colour of the flame depends on the metal in the salt used.į As an extension, students can view the flames through hand-held spectroscopes or diffraction gratings in order to see the line spectrum of the element. Repeat with the other bottles.Į A spectacular coloured flame or jet should be seen in each case. Spray the solution into the flame in the direction you have rehearsed. Procedureī Light the Bunsen and adjust it to give a non-luminous, roaring flame (air hole open).Ĭ Conduct a preliminary spray in a safe direction away from the Bunsen flame.Īdjust the nozzles of the spray bottles to give a fine mist.ĭ Choose one spray bottle. Barium chloride is toxic but gives a different colour (refer to CLEAPSS Hazcard), while calcium chloride ( Irritant) and strontium chloride ( Irritant) are different again (refer to CLEAPSS Hazcard). those of calcium and barium) can also be used provided an appropriate risk assessment is carried out. These two are in fact a little more volatile than the chloride, and potassium iodide is certainly likely to be available (refer to CLEAPSS Hazcard). As a general rule, chlorides are usually suggested as they tend to be more volatile and more readily available. They can be stored in the plastic bottles for several weeks at least without apparent deterioration of the bottles.ģ Potassium iodide and lithium iodide can be used instead. The solutions can be retained for future use. Place each solution in a spray bottle and label the bottle. To do this, add the salt to the ethanol in small quantities, with stirring, until no more will dissolve – often only a few mg of salt will be needed. Make a saturated solution of each salt in about 10 cm 3 ethanol. Never use spray bottles with a rubber bulb - the flame may flash back into the container.Ģ The chlorides of metals are the best but other salts also work. Ideally, one bottle is needed for each metal salt. These piston-operated spray bottles should be emptied, cleaned thoroughly and finally rinsed with distilled water. Do NOT be tempted to use the more toxic and volatile methanol in place of ethanol.ġ Spray bottles of the type used for products such as window cleaner should be used. IDA (industrial denatured alcohol) is Highly flammable, Harmful. Copper sulfate is Harmful, Danger to the environment.Ensure that the spray can be safely directed away from yourself and the audience. Read our standard health & safety guidanceĬarry out the whole experiment in a well-ventilated area you have previously shown to be safe. ![]() Refer to Health & Safety and Technical notes section below for additional information. Potassium chloride (Low hazard) (see note 3)Ĭopper sulfate (Harmful, Danger to the environment)Įthanol (Highly flammable), approx 10 cm 3 for each metal salt, or IDA (industrial denatured alcohol) (Highly flammable, Harmful) Samples of the following metal salts (no more than 1 g of each) (see note 2): Hand-held spectroscopes or diffraction gratings (optional) Trigger pump operated spray bottles (see note 1) Preparation includes making up the spray bottles and conducting a risk assessment. Your employer’s risk assessment must be customised by determining where to spray the flame to guarantee the audience’s safety. It takes about ten minutes if all is prepared in advance. This experiment must be done as a demonstration. It can be extended as an introduction to atomic spectra for post-16 students. This is a spectacular version of the ‘flame tests’ experiment that can be used with chemists and non-chemists alike. This demonstration experiment can be used to show the flame colours given by alkali metal, alkaline earth metal, and other metal, salts. RSC Yusuf Hamied Inspirational Science Programme.Introductory maths for higher education.The physics of restoration and conservation.
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