- Edible salt, its preparation and uses.
- Baking soda/ powder, its preparation and uses.
- Vinegar, its preparation and role to preserve foods.
- A brief discussion on soft drinks.
we use different kinds of chemical substances such as table salt, baking powder, vinegar, and soft drinks in our houses.
Table Salt or Edible salt
Sodium chloride (NaCl) is known as table salt or edible salt.
Preparation of Table Salt
NaCl along with a little quantity of some other salts including MgCl2 are dissolved in sea water at a larger scale. Again sufficient sodium chloride (NaCl) is found in the underground as minerals. Various country like Bangladesh, table salt is extracted from sea water.
Firstly, salt cultivators in the coastal areas of Bangladesh make dams around the square or rectangular land of different sizes and keep a small empty space in every of them to enter the tide water. Then closing the entry point tide-water is reserved inside. When this water gets emaciated in sunlight salts become visible there. This method is called salt harvesting. This type of salt obtained contains sand. So, it is further treated through the different process in factories to convert it into edible salt.
Secondly, when the salt is mixed with water in a pot, it is dissolved in water but the sand remains at the bottom of the pot. Then the salt-water solution is separated through ﬁltration.
Salt harvesting in the coastal area
Thirdly, when this sand free salt-water solution is heated, the water vaporizes but the salt remains at the bottom of the pot. In this way, the processed salt is packed and sent to the different places for sales.
Uses of NaCl
(i) Our body needs different types of ions like Na+, K+ etc. for all normal activities in our body. If there is any lacking of Na+ in our body due to any reason, this deﬁciency is ﬁlled up by taking NaCl with water.
(ii) We eat rice with curry. The curry does not taste good if we do not use NaCl salt in it.
(iii) NaCl is used in industries to prepare NaOH compound.
(iv) NaCl is widely used in drug industries to manufacture salines for diarrhoea or dehydration.
The chemical name of baking soda or table soda is sodium hydrogen carbonate (i.e. NaHCO3).
Preparation of Baking Soda
Firstly, a saturated solution of NaCl is prepared by dissolving NaCl in water. Secondly, this saturated solution is further saturated by blowing NH3 gas into it. Finally, CO2 gas is blown into NaCl solution saturated by NH3. In this stage, at ﬁrst CO2, NH3 and H2O together produce Ammonium Hydrogen Carbonate (NH4HCO3).
Then, this NH4HCO3 reacts with sodium chloride and produces sodium hydrogen carbonate or baking soda (NaHCO3). Baking soda is separated from the reaction pot. When the tartaric acid (C4H6O6) is mixed with baking soda (NaHCO3). This mixture is called baking powder.
Uses of Baking Soda
Baking powder is usually used in making cakes. During making cakes, it is mixed with the ﬂour of cake and heated. Now, do you know why does the cake rise/ swell up?
This is because, baking soda reacts with tartaric acid (C4H6O6) in the mixture to produce sodium tartrate (C4H4Na2O6), CO2 gas and H2O. Here, cakes rise up because of this CO2 gas.
Sometimes we use one type of fungus named ‘Yeast’ in our home or bakeries to inﬂate bread. To do this, yeast is added to a solution of sugar initially. If the dough is made with this yeast- sugar mixture solution and kept in a warm place then CO2 is produced due to aerobic respiration of the yeast. Hence, this CO2 helps the cakes to swell up. When the bread is baked in the oven after sufﬁcient blow-up then the yeast dies in heat and the blow-up process of bread stops.
Vinegar is a liquid substance. 4% to 10% liquid solution of ethanoic acid (acetic acid) is called Vinegar.
Preparation of Vinegar
It is prepared by blowing the bubble of oxygen gas into ethanol and acetobacter is kept in a steel pot at (25-35) °C temperature.
Roles of Vinegar in Preserving Food
Pickles get putrefied or rotten if bacteria attack them. But if vinegar is applied to them, bacteria cannot attack them. We know the main element of vinegar is ethanoic acid. The protein released by ethanoic acid damages H+ bacteria. As a result, the foods remain safe from the attack of bacteria. In this way, food is preserved by using Vinegar.
A soft drink typically contains carbonated water, a sweetener, and a natural or artificial flavouring. The sweetener may be sugar, fruit juice, high-fructose corn syrup, sugar substitutes or some combination of these.
Soft drinks are prepared when carbon dioxide gas is dissolved in water at the cold state and high temperature. CO2 and H2O react in the soft drink to produce H2CO3. Some examples are coca-cola, sprite etc. People take soft drinks for the digestion of food.
*References: NCTB, Google and Wikipedia.