Monthly Archives: September 2014
Our blog is normally reserved for science news & facts and other interesting things! However we thought we’d share this video featuring the new range of Ohaus Adventurer balances. With dual USB ports, one at the front and one at the back connectivity is easy. With colour touchscreen, fast stabilisation and accuracy these balances are worth a look. Visit our website news page on the link below to download a brochure.
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Back in your school days there was probably an experiment where you placed a small amount of a compound into a flame and observed it’s colour. This is the flame test and depending on the colour observed it can tell you what elements are present.
Scientifically put, A flame test is an analytic procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element’s characteristic emission spectrum. The colour of flames in general also depends on temperature.
The test involves introducing a sample of the element or compound to a hot, non-luminous flame, and observing the colour of the flame that results. The idea of the test is that sample atoms evaporate and since they are hot, they emit light when being in flame.
The flame test is relatively quick and simple to perform, and can be carried out with the basic equipment found in most chemistry laboratories. However, the range of elements positively detectable under these conditions is small, as the test relies on the subjective experience of the experimenter rather than any objective measurements. The test has difficulty detecting small concentrations of some elements, while too strong a result may be produced for certain others, which tends to cause fainter colours to not appear.
|Metal Ion Flame Tests-Click to enlarge|
The table above from www.compoundchem.com shows the range of colours chemicals produce. These tests work better for some metal ions than other; in particular, those ions shown on the bottom row of the infographic are generally quite faint and hard to distinguish. Sodium’s flame colour is also very strong, and can easily mask the colours of other metal ions.
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|Click to enlarge|
Various methods have been used since to produce this but the modern method, the Hooker process, is the only one producing this in any bulk capacity.
Sodium Hypochlorite has many uses as can be seen above:-
In bleach cleaning products and to remove stains.
In Swimming pools as a disinfectant.
In Antibacterial sprays
To neutralise nerve agents
To reduce skin damage – using very low concentrations.
Sodium Hypochlorite although used in household bleach is not the only component. There is often Sodium Hydroxide and Calcium Hypochlorite amongst others. it must be remembered not to mix household cleaning products as some may contain hydrochloric acid. If these are mixed with bleach, it can react with sodium hypochlorite, and form toxic chlorine gas
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Where did the summertime break go? Time for kids to go back to school. And time for us too…chemistry basics…..Acids and bases
- have a low pH (1-6) – the lower the number the stronger the acid
- react with bases to form neutral compounds
- are corrosive when they are strong
- are an irritant when they are weak.
Acids have a pH of less than 7. Bases have a pH of more than 7. When bases are dissolved in water, they are known as alkalis. Salts are made when an acid reacts with a base, carbonate or metal. The name of the salt formed depends on the metal in the base and the acid used. For example, salts made using hydrochloric acid are called chlorides.
Substances with a pH of less than 7 are acids. The more strongly acidic the solution, the lower its pH number. Acidic solutions turn blue litmus paper red. They turn universal indicator paper red if they are strongly acidic, and orange or yellow if they are weakly acidic.
Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide are bases.
Bases that dissolve in water are called alkalis. Copper oxide is not an alkali because it does not dissolve in water. Sodium hydroxide is an alkali because it does dissolve in water.
Alkaline solutions have a pH of more than 7. The stronger the alkali, the higher the pH number. Alkalis turn red litmus paper blue. They turn universal indicator paper dark blue or purple if they are strongly alkaline, and blue-green if they are weakly alkaline.
Neutral solutions have a pH of 7. They do not change the colour of litmus paper, but they turn universal indicator paper green. Water is neutral.
For pH meters or pH test papers or buffer solutions give us a call.
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