Dr. Jayasimha

 

Carrots Cherries and cherry juice is bright red in acidic solution but purple to blue in basic solution. Cranberries Curry powder and tumeric are spices that contain a bright yellow pigment called curcumin (which is not an anthocyanin). It turns from yellow at pH 7.4 to red at pH 8.6. Delphinium petals contain an anthocyanin called delphinin, which changes from bluish red in acid to blue to violet in basic solution. Red cabbage contains a mixture of anthocyanins and other pigments that indicate a wide range of pH. The photograph at right shows how red cabbage juice changes from deep red at pH 1 to purple at pH 7 to to green at pH 12. At higher pH (13-14) it turns yellow. Red radish Rhubarb Rose petals contain the oxonium salt of cyanin, and they turn blue in basic solution. (The potassium or calcium salt of the same pigment makes cornflowers blue!) Strawberries Tea

Methyl orange is synthesized by diazotization. Methyl orange is synthesized by reaction of sulfanilic acid, sodium nitrite, and dimethylaniline. First, sulfanilic acid is dissolved in dilute aqueous acid. Sodium nitrite is added to produce a diazonium salt .The diazonium salt is then coupled with dimethylaniline. The coupling takes place in the opposite ("para") position from the -N(CH3)2 group: The sodium acetate makes the solution weakly basic; the acetate ion accepts the hydrogen displaced from the dimethylaniline ring.