Honey is adulterated by way of adding jiggery syrup. To verify whether honey is pure, take a glass of water and pour one tablespoon of honey in it. Gently shake the glass (note not to stir). If the honey completely dissolves in water it is adulterated, On the other hand if it stays as a mass, it is pure honey.
Generally a substance dissolved in a liquid lowers the freezing point or melting point of that liquid. When salt is added to ice at room temperature, some of the ice melts and cools the salt to zero degrees Celsius. The salt solution produced cannot remain in equilibrium with ice at zero degrees. It is possible only when the ice is at the freezing point of the solution (less than 0 degrees Celsius). So more ice in contact with the salt solutions melts taking the necessary latent heat of fusion from the salt solution, whose temperature is consequently lowered.
More salt thus dissolves, keeping the solution saturated and the process continues till the temperature of the solution reduced to -21 degrees Centigrade. Only at this point (eutectic point) ice is in equilibrium with saturated salt solution. When 23 per cent of salt is added to ice, the freezing point is lowered to -21 degrees.
Solid ice exists at zero degrees Celsius and salt at room temperature which is bound to be higher. So, when the two mix, ice begins to melt. But the temperature still remains at zero. A little of the salt dissolves in the water thus formed. In this process, the fine, solid particles of salt breaks down to positive sodium ions and negative chloride ions (dissociation). This change requires energy which is absorbed from the solution which is cooled below zero degrees Celsius. As more and more salt dissolves, temperature goes down further till -21 degrees Celsius is reached. At this stage, the solution is saturated, that is, the maximum solubility of salt at that temperature has been attained. Ice, solution and salt co-exist at this point called eutectic point.
This principle is used in making freezing mixtures which provide sub-zero temperatures. If calcium chloride is employed instead of sodium chloride, temperatures as low as -55 degrees Celsius could be obtained.
Another application of salt and ice is in de-icing of roads during winter. The smooth, slippery surface of ice is dangerous to fast moving vehicles. When salt is thrown on the ice, it dissolves and the solution though at a low temperature flows away leaving the roads free. Because of the presence of about 3 percent of salts (chiefly common salt) sea water freezes at -2 degrees Celsius instead of at zero.
Salt is used to melt ice on roads and sidewalks. On contact with ice, some of the salt dissolves.
The salt solution has a lower freezing point than pure ice and exists as a liquid at zero degrees Celsius. So even on a cold day, the ice can be melted drained using salt.
One can use sodium chloride (common salt) and calcium chloride for the above purpose. The depression of the freezing point depends on the number of particles in a given amount of solvent.
Electrolytes are compounds which produce ions in solution. NaCI exists as a sodium ion and a chloride ion in solution and calcium chloride as a calcium ion and two chloride ions. Among these the calcium salt is better clearing ice from sidewalks as it produces more particles (three ions – one calcium ion and two chloride ions) in the solution. But we cannot use them for cleaning ice in automobile radiators because of their corrosive nature. For that ethylene glycol is used as antifreeze even though it is not as efficient as the calcium salt.
