Kuhinjska so NaCl
Kuhinjska so ili natrijum hlorid čija je molekulska formula NaCl je jedno od najrasprostranjenijih hemijskih jedinjenja u prirodi. Natrijum hlorid je bela kristalna supstancija, veoma dobro rastvorljiva u vodi, sa malom maksimalnom koncentracijom. Molekul natrijum hlorida se sastoji od jednog atoma natrijuma i jednog atoma hlora. Molekulska masa kuhinjske soli je 58.4 u. Temperatura topljenja natrijum hlorida iznosi 801 °C, a temperatura ključanja 1465 °C.
Biološki značaj soli
Kuhinjska so je glavni izvor jona Na+ i Cl- za ljude i životinje. Joni Na+ imaju ključnu ulogu u mnogim fiziološkim procesima od održanja stalnog krvnog pritiska do održanja rada nervnog sistema.Čovek često koristi kuhinjsku so u svojoj ishrani kao začin ili kao sredstvo koje utiče na kvalitet i brzinu pripremanja hrane. Unošenje kuhinjske soli je neophodno za život. Dnevne potrebe za njom iznose oko 50 mg ali u današnjim uslovima unosi nekoliko puta više. Optimalna količina od 50 mg soli nalazi se u jednoj vekni običnog belog hleba. Pretpostavlja se da preterana upotreba soli može da izazove pojavu nekih oboljenja.Nedostatak joda u ishrani i u vodi izaziva bolest pod imenom gušavost ili struma. Ovo oboljenje se uglavnom javlja kao endemska guša (endemska struma) u krajevima udaljenim od mora, tamo gde se ne dodaje jod u kuhinjsku so. Kuhinjskoj soli se dodaje kalijum-jodid radi sprečavanja gušavosti.
Upotreba soli
So se najviše koristi u hemijskoj industriji čak 45%. Upotrebljava se za dobijanje hlora i njegovog koprodukta natrijumovog hidroksida, ali i za dobijanje deterdženata, sapuna ili šampona. U farmaciji se koristi kao hemijski reagens. Na hranu se potroši 4% i to u obliku pojačavača ukusa, konzervansa ili vezivnog sredstva. U meso se dodaje da bi se sprečila pojava bakterija, u konzerve kao konzervans, a u sir kao kontrolno sredstvo.
ZANIMLjIVO Istorijat upotrebe soli
Praistorijske civilizacije nisu bile svesne svoje potrebe za solju. Legenda iz Mesopotamije govori o ranjenoj svinji koja je pala u okean i utopila se. Nakon što su je izvadili i probali, zaključili su da je ukusnija nego nezasoljeno meso. Sumerijanci su solili meso i koristili so da bi sačuvali hranu čak 3500 godina pre nove ere. A trojanci su 1000 godina pre nove ere naučili da koriste so da bi sačuvali ribu. Zanimljiv je primer da je i rimski vladar Pompej dodavao so u svoje piće kao navodni protivotrov za otrove. So je tokom godina postajala sve cenjenija i označavala je često vrednost i značaj pojedinih porodica. S vremenom se čak i plata isplaćivala kroz so. Tako je i nastao naziv salary (eng. plata) od latinske reči salt što znači so.
Table salt or sodium chloride, whose molecular formula is NaCl, is one of the most widespread chemical compounds in nature. Sodium chloride is a white crystalline substance, very well soluble in water, with a low maximum concentration. Sodium chloride molecule consists of one atom of sodium and one atom of chlorine. The molecular weight of NaCl is 58.4u. Melting point of NaCl is 801°C, and its boiling point is 1465°C.
Biological significance of salt
Table salt is the main source of ions Na+ and Cl– for humans and animals. Na+ ions play a key role in many physiological processes, from maintaining blood pressure constant to maintaining the functioning of nervous system. People often use table salt in their diet as a condiment or as a means which affects the quality and speed of food preparation. Intake of salt is essential for both human and animal life. The daily need for it is about 50 mg, but nowadays we take in several times as much. Optimal amount of 50 mg of salt can be found in a single loaf of white bread. It is assumed that excessive use of salt can cause some diseases. Iodine deficiency in diet and in water causes the disease known as goiter or struma. This disease usually occurs as endemic goiter in regions distant from the sea, where iodine is not added to table salt. Potassium iodide is added to table salt in order to prevent goiter.
The use of salt
Table salt is most widely used in the chemical industry, no less than 45%. It is used for obtaining chlorine and its by-product sodium hydroxide, but also for getting detergents, soaps or shampoos. It is used as a chemical reagent in pharmaceutics. Only 4% of salt is spent on food in the form of flavor enhancers, preservatives or binders. It is added to meat to prevent the emergence of bacteria, it is put into cans as a preservative, and it is added to cheese as a control agent.
INTERESTING History of the use of salt
Prehistoric civilizations were not aware of their need for salt. A Mesopotamian legend tells a story of a wounded pig that fell into the ocean and drowned. Once they took it out of the water and tasted it, they concluded that it tasted better than unsalted meat. The Sumerians added salt to meat, and they used salt to preserve food, as early as in 3500 BC. In 1000 BC, the Trojans learned how to use salt to preserve fish. An interesting example is the Roman emperor Pompey who added salt to his drink as, apparently, an antidote to poisons. Over the years, salt became more and more valuable and it often denoted the worth and significance of particular families. In time, even the wages were paid in salt, hence the word salary from the Latin word salt meaning salt.
