Citric acid and sodium chloride are chemically different. However, these compounds share several important features. Both are found naturally in all living organisms, and both are preservatives. They are in fruits and vegetables, as well as in processed foods. Just like sodium chloride, citric acid occurs in a white crystalline form, although it can occur as a white power as well.
Citric Acid -- Chemistry
Citric acid is an weak organic acid, just like vinegar. This is not a toxic chemical. The oral LD-50 of citric acid in rats is between 3 and 5 g/kg, depending upon how it is administered. LD-50 refers to the lowest possible dose of a chemical that will kill 50 percent of the animals to which it is administered.
Lemon and lime juice provide more citric acid than grapefruit or orange juice. Occasionally it will appear on labels under the names sour salt, citric acid hydrate and 2-hydroxy-1,2,3-propanetricarboxylic acid monohydrate.
Citric Acid -- Uses
The UK Food Guide points out that since citric acid serves both as a preservative and a taste-enhancer, it is in many foods, including “non-alcoholic drinks, bakery products, beer, cheese and processed cheese spreads, cider, biscuits, cake mixes, frozen fish, ice cream, jams, jellies, frozen croquette potatoes and potato waffles, preserves, sorbets, packet soups, sweets, tinned fruits, sauces and vegetables and wine.”
Sodium Chloride Chemistry
Sodium chloride, or ordinary table salt, dissociates into sodium and chloride ions when dissolved in water. Ions are charged particles. The charge on these particles is part of the reason sodium chloride is essential to life. The different concentrations of the positively charged sodium and potassium ions on either side of neuronal membranes makes it possible for one nerve to conduct signals to another.
Blood Pressure Regulation
Sodium chloride is also essential to the regulation of blood pressure. Sodium levels determine the volume of fluid outside the cells. Consuming too much sodium chloride causes the levels of extracellular fluid to increase, which, in turn, increases the pressure on the walls of blood vessels. The relationship between sodium and blood volume is why doctors urge patients with high blood pressure to use less salt.