Indigo Blue

Brief Overview 

Hydrochloric acid is a clear, colorless, highly pungent solution of hydrogen chloride (HCl) in water. It is a highly corrosive acid with many industrial uses. It is a monoprotic acid and is less likely to undergo an interfering oxidation-reduction reaction than other industrial acids. Despite its acidity, it is one of the least hazardous strong acids to handle, as it contains the non-reactive and non-toxic chloride ion. Intermediate-strength hydrochloric acid solutions are quite stable upon storage, and their concentrations are maintained over time. These attributes, together with the fact that it is available as a pure reagent, make hydrochloric acid an excellent acidifying reagent.

Manufacturing Process

Indigo dye is made from the leaves of Polygonum Tinctorium. The indigo leaves are fermented for 2 to 3 months into a black clump with 2 - 10 % of indigo pigment. Wood ash, lime and bran are then mixed with the indigo clump and subjected to further water mixing, heated to 30~40℃, and then dried to form insoluble blue indigo.

Indigo is subjected to sulfonation with concentrated sulfuric acid, followed by dilution and then neutralization with soda ash. Sodium chloride is then added for salting out, before the mixture is filtered, washed and dried to get the finished product.

Food Industry

Hydrochloric acid is used as an acidifier for products such as sauces, vegetable juices, cornstarch, and canned goods. Hydrochloric acid is used in acidulating crushed bones to manufacture gelatin. It is also used in the production of artificial sweeteners. In other food processing applications, hydrochloric acid is used to production of hydrolyzed vegetable protein and soy sauce.

Metallurgy Industry     
                                
Hydrochloric acid is used in producing chlorides in the hydrochlorination process, polymerization process, and isomerization process. It is also used for refining ore in the production of tin and tantalum, pickling and cleaning metal products, electroplating, removing scale from boilers, and neutralizing basic systems.

Other Applications

Hydrochloric acid is used to adjust the pH of intermediates, final products, and wastewater. It is also used in the oil industry in petroleum wells' acidification (activation). It is used to produce lysine, choline chloride (both mainly used as animal feed additives), and citric acid.