Salt is existent in all animal and vegetable life and is coeval with life itself. It must have been present in the first herbage that gave nourishment to the first beast. The history of salt is thus the history of civilization on earth. The Roman legions were paid money for salt and from Sal-dare (to give salt) is derived the Latin word salarium meaning “salt money”. Cakes of salt have been used as money in Abyssinia and in some other parts of Africa. The Sanskrit word for salt is “lavana” to which ‘Nun’, the common Punjabi word for salt, owes its origin, susruta, the father of Indian medicine, speaks of four kinds of salts which respond with rock salt, sea salt, lake salt and earth salt respectively. Egyptians salted ducks, quails and sardines, they also preserved the boiling of salt of their illustrious dead (Egyptian mummies) in salt. The Babylonians also knew the use of salt. Even now salt is produced in china in solar evaporation. In Japan the manufacture of salt by boiling etc we introduced some 2000 years ago. The age-old adage ‘worthy of his salt’ or ‘true eto his salt’ proves the importance attached to this commodity from times immemorial. We find present day conversations salted down so to speak with similes such as the expression: “take that statement with a grain of salt”, what the man really means is to make allowance for stretching of the truth. Mythology and religion have been flavored with salt. Gods were worshipped as the providers of bread and salt. In India manufacture of salt along the seacoast in Bengal, Bombay, Madras and the rann of Kutch, flourished as a cottage industry for centuries. In his “Early History of Bengal”, Mr. Manahan gives passage from ‘Arthasastra’ – Book dealing with the history of the Mauryan period (300 B.C)- which says that salt manufacture was even at that distant date supervised by a State Official named ‘Lavanadhyaksa’ and the business was carried on under a system of licenses granted on the payment of fixed fees or part of the output.



Common Salt – Properties and Uses

        Sodium chloride (Nacl) now called common salt is an example of the simplest type of chemical salt. a molecule of common salt contains an atom of chlorine combined with 23 parts by weight of sodium to form 58.5 parts of common salt., Rock salt is rarely found in an absolutely pure anhydrous state in which it is colourless and perfectly transparent. In most rock salt, mines such specimens are considered curiosities. In Wieliczka mine in Poland and in Khewra mine in the Punjab large masses of salt containing over 99 percent Nacl are met with. In the Punjab mines we meet with salt of different colours such as white, pink, darkish or red. The colour disappears when salt is crushed to powder. The colour of seawater is affected by the percentage of salt in it; as the quantity of salt decreases, the colour changes from blue to green. Salt is met with in any colours; white, pink, red, brown, greenish and grey. The red or green colour is attributed to the presence of infusoria.

        Salt is highly soluble in water, 100 parts of which dissolve 37 parts of salt. The specific gravity of such solution 1:2, the specific gravity of salt crystals is 2.16. The smallest quantity perceptible to taste is 68 grains of salt dissolved in a gallon of water.

        Pure Sodium Chloride is not deliquescent. It, however, absorbs moisture owing to the presence of magnesium chloride.

        Sodium Chloride melts at very high temperature, at still higher temperatures it evaporates and at white heat it volatilizes forming thick clouds. It does not diffuse much, even when masses of varying densities are super-imposed on one another.

        Salt is fairly hard. there is no standard unit fixed for hardness. Geologists, however, compare the hardness of minerals by a comparative table (Moh’s table of hardness) according to which the hardness of talc is considered as one and that of diamond ten. According to this standard the hardness of salt is 2.5. Its cohesion or power of supporting pressure is twice as great as that of bricks.

        Common salt is a crystalline substance: crystals generally form cubes and sometimes they form octahedrons. The form of crystals depends on temperature, state of rest or motion, length of time etc. Salt has a perfect cleavage. It splits up readily in to planes parallel to the faces of the cubes of which it is composed.

        Salt has acoustic properties as well that is to say; it is a good medium for the transmission of sound. Workmen in a salt mine are able to signal by blows on the face of the rock. Salt possesses in a high degree the power of staying decomposition in dead organisms and is the commonest of all preservatives. Owing to this property it is an absolute necessity to the life of man and the higher animals.

        Salt water trickling through the roof of a working also forms stalactites and stalagmites just as time-stone forms them. In Khewra mine we meet with long hollow tubes of salt formed by the brine trickling drop by drop through the roof.

        Rock salt has many minerals associates with it: for instance, gypsum, sodium sulphate, magnesium sulphate and magnesium chloride. In the Khewra mine, salt is found mixed with variously cioloured clays, white pink, red, variegated gypsum beds, limestone, and magnesium sulphate. Bad salt is associated with magnesium sulphate and good salt with calcium chloride. A cube foot of pure rock salt weight about 25 to 27 kgs. 
    
        Common salt is a necessity of life. It imparts an agreeable flavour and improves the taste of food and is used as a condiment. it may be interesting to know how exactly salt consumed in its natural or artificial form functions in the human body. It is Iodised by infusion of minute doses of potassium iodide about .02% as prophylaxis for Goitre Similarly, it is medicated with phosphates or other ingredients to regulate the deficiencies in human system. Salt, in short, is a preserver health. Lord Lawrence, in his evidence before the Select Committee on East India Finance in 1873, attributed the prevalence of murrain in the Indian cattle to the want of salt in their food. It was used as chemical manure long before the Christian era and its value was recognized throughout Europe. the ancient Hebrews applied it as a manure over 2,000 years ago in Palestine and so did that eminently agricultural people in Chinese and do still to this day. The old Romans too used it as manure. In India its use in agriculture is rather looked on with disfavour. Mr. Arthur Young, an outstanding figure in the history of English and even European agricultural renaissance, considered salt of great value as fertilizer.

        The use of salt in modern industries is equally or perhaps more important. A number of arts and manufacturers of modern civilizations owe their existences to salt. In short, salt is indispensable to industrial advance.