Monthly Archives: June 2012
The number of chemicals in the home abound. Chemistry is at work in the bathroom, kitchen, laundry and medicine cabinet. Sodium bicarbonate is a most useful, versatile and cheaply available substance used in the home and for personal use.
Sodium bicarbonate is obtained by chemical process called the Solvay Process, or more directly by extraction from the ore. It is mildly alkaline and has a wide range of applications.
Sodium bicarbonate has the chemical formula CHNaO3. It is known under different household names: baking soda, sodium bicarb or bicarb soda, etc. but better known to chemists as sodium bicarbonate, bicarbonate of soda, sodium hydrogen carbonate, and sodium acid carbonate.
History of Production
The ancient Egyptians first mined the natural deposit called natron, which contains mostly sodium bicarbonate. The mixture was used as a cleansing agent such as soap. It was not until 1791 in France that Leblanc artificially manufactured sodium bicarbonate as we know it today. Later, in 1846, two bakers Dwight and Church refined the process of making baking soda from sodium carbonate and carbon dioxide. The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s.
Baking soda is mainly prepared from the Solvay Process. However, commercial quantities are also produced from soda ash of the ore trona, which is dissolved in water and treated with carbon dioxide. Sodium bicarbonate then precipitates as a solid. The main reaction is:
Na2CO3 + CO2 + H2O -> 2NaHCO3
Sodium bicarbonate has a number of interesting properties, which makes it so versatile and useful:
- Odourless, white crystalline solid or powder
- Slightly alkaline in solution
- Sparingly soluble in water
- Decomposes to sodium carbonate and carbon dioxide on heating
- Has relatively low toxicity
- The powder dust is not explosive
Applications of Baking Soda
Baking soda is a weak base and therefore not a powerful detergent compared to a strong alkali which breaks down fat. However, it does remove dirt with the properties already alluded to. In order to prevent any alkali from damaging your skin, rubber gloves should be worn.
For the Home:
- Cleaning agent – fridges, garbage disposals, etc.
- Water softener – use in washing machines and for washing dishes
- Deodorizing – shoes, footwear cupboards, carpet refresher
- Fire extinguisher – forms a smothering soapy foam
- Polishing – removes dirt without damaging high hardness materials such as stainless steel or iron
- Mixed with sugar – acts as an effective pesticide for cockroaches and silverfish
In the Kitchen:
- Baking – used as a leavening agent, the carbon dioxide generated makes the dough rise
- Cooking – quickly softens vegetables such as french beans and broccoli
For Care of the Body:
- Use as a teeth whitener – brush teeth with a paste of bicarb soda and water
- Sodium bicarbonate ear drops
- Stomach reliever – spoonful in cool glass of water
- Eczema reliever – half-cup in hot bath from 15 to 20 minutes
- Also good for the throat, painful gums, insect bites, and warts
- Use in cosmetics and personal care products
Sodium bicarbonate can neutralise or reduce acids in the blood, or urine. It may be used in emergency medical situations (heart attacks, serious kidney or lung problems) to correct the normal acid-base balance in the blood or as an aid in treating overdoses with certain types of medications.
Impurities in Sodium Bicarbonate
Sodium bicarbonate is a very versatile substance and the list of uses given is by no means exhaustive, but represents some of the better known uses. People should be aware that when using for medicinal purposes, producer’s baking soda contains traces of aluminium. P&R Labpak recommend you seek medical and/or other advice before using such a product for any kind of personal use.
- Place an open box or small open container of bicarbonate of soda in the refrigerator or pantry to absorb odours. Replace every three months.
- Eliminate odours in dishwashers by running a cycle without any dishes once a week with bicarb soda in the soap dispenser and vinegar in the rinse-aid compartment. Sprinkle a handful in the bottom of the dishwasher between loads. It will reduce odours and act as an additional cleanser for the next wash.
- Clean tannin-stained tea and coffee mugs by sprinkling some bi-carb soda on a damp cloth and rubbing gently.
- For saucepans that cannot be cleaned with scourers, add cold water and one to two tablespoons of bicarb soda. Bring to the boil and simmer for a few minutes. Empty water from pan and use a steel scourer to remove any residue (ensuring saucepan has had time to cool sufficiently to handle safely).
- To eliminate odours and reduce drain blockages, put half a cup of bi-carb soda and half a cup of vinegar down the kitchen sink drain. Leave for at least an hour then rinse with boiling water (use hot water only for plastic pipes).
Using Bicarbonate of Soda in the Laundry
- Dissolve two to three tablespoons of bicarb soda in a bucket of warm water to pre-soak cloth nappies and/or items with mould or stubborn stains. Allow to soak, then wash items in warm soapy water and dry in the sun.
- As a natural laundry whitener, use 2 teaspoons of bicarb soda in half a bucket of cold water. Soak items for 30 minutes then wash as usual.
- Add half a cup to the washing machine for the rinse cycle to keep clothing and linen fresh.
General Cleaning with Sodium Bicarbonate
- Sprinkle sodium bicarbonate into smelly sports shoes and leave for a few days to reduce foot odour.
- Make a paste with three parts sodium bicarbonate to one part water (adjust to suit individual needs). Use as an alternative to other paste cleansers.
- Sprinkle carpets with sodium bicarbonate, leave for a few minutes, then vacuum as usual to help eliminate household odours. This also works on pet bedding and car upholstery. Sprinkle and leave for 15 minutes before vacuuming.
- Freshen children’s stuffed toys by sprinkling with bicarb soda. Leave for 15 minutes, then brush off residue.
Atomic Timekeeping (A fantastic fact sheet from the NPL – National Physical Laboratory)
Check out their website for more great factsheets – www.npl.co.uk
The spinning Earth gives our most basic measurement of time – the day – and for thousands of years it was our most stable timekeeper.
However, the quartz and atomic clocks invented during the 1930s and 1950s are even better timekeepers which show that the Earth does not rotate steadily but wobbles!
NPL built the world’s first working caesium atomic clock in 1955 and paved the way for a new and better definition of the second based on the fundamental properties of atoms.
How an Atomic Clock Works (Theory)
The atom can be pictured as a mini solar system, with the heavy nucleus at the centre surrounded by electrons in a variety of different orbits.
The orbits correspond to energy levels, and electrons can only move between levels when they absorb or release just the right amount of energy.
This energy is absorbed or released in the form of electromagnetic radiation, the frequency of which depends on the difference in energy between the two levels.
This transition is the source of the term “quantum jump”, quantum referring to the tiny but precise amount of energy needed to allow the electron to jump to a different level.
By measuring the frequency of the electromagnetic radiation, like counting the number of pendulum swings on a pendulum, we can measure the passage of time.
How Long is a Second?
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
How do you Keep Time Around the World?
Everyone around the world needs to keep to an agreed timescale.
On the 1st January 1972, Coordinated Universal Time (UTC) was adopted as the official time for the world.
The International Bureau of Weights and Measures (BIPM) acts as the official time keeper of atomic time for the world.
There are 65 laboratories with over 230 clocks contributing to the international timescale.
As BIPM counts the seconds astronomers still continue to measure time by the rotation of the Earth about its axis. This is compared to UTC, and if these measurements differ by more than 0.9 seconds a leap second is added or subtracted to keep the timescales together.
Quantum standards are based on fundamental properties of matter.
In the case of the atomic clock this is the energy released when electrons move between energy levels of a caesium atom.
Using the movement of the Earth to define the second is a problem because this varies unpredictably with time, so the length of a second defined this way would not be constant.
But quantum standards, as far as we know, will be stable forever, no matter when or where it is measured.
Thousands of years in the future, or in a distant galaxy, the energy levels of the caesium atom are exactly the same, and so is the length of the second defined in this way.
Why do we Need the Accuracy of Atomic Clocks?
Time measurement has become a basic part of everyday life and accuracies of the nearest minute or a few seconds are usually good enough for most human activities, but highly accurate timing plays a vital role in many other aspects of the modern world.
The Global Positioning System (GPS) satellites broadcast timing signals from onboard atomic clocks, which enable land vehicles, shipping and aircraft to know their location within a few metres.
Other people making use of GPS include ecologists tracking the movements of rare animals, prospectors, surveyors, mountaineers, and the search and rescue teams if any of these pursuits go wrong.
Research is underway to make specialist location systems accurate to within millimetres.
Access to the national time scale, UTC(NPL)
NPL has been disseminating the UK national time scale from a transmitter at Rugby since 1950. The signal now comes from Anthorn in Cumbria.
This transmitter, which has the call sign MSF, operates 24 hours a day at a frequency of 60 kHz; transmissions can be received as far away as Iceland and Gibraltar.
Alternatively you can connect to the NPL timescale over the internet from anywhere in the world, and set your PC or Mac to UTC(NPL).
Visit our Computer Time Services page.
How an Atomic Clock Works (Practice)
In 1955 Louis Essen built the world’s first caesium atomic clock at NPL.
Today a new form of atomic clock, the caesium fountain, is being used. In this clock, a cloud of atoms is projected up into a microwave chamber and allowed to fall down under gravity.
The fountain uses laser beams to slow down the atoms.
The slow movement of the atoms allows a more accurate measurement of the transition between energy levels and hence the frequency of radiation.
The Next Generation
Clocks for the 21st century are being developed in the form of ion traps.
Ions are charged atoms which can be trapped by electromagnetic fields almost indefinitely. Once trapped a laser beam can then be used to cool the ion down close to absolute zero, keeping it stationary.
At NPL the element strontium has been chosen to develop ion trap clocks as its ions can have very stable states. These clocks may have accuracies of around 1000 times higher than the best current atomic clocks.
That is equivalent to losing no more than one second in the lifetime of the universe.
The link below is a table showing the physical properties and chemical resistance of plastics including its care and maintenance. Click here