2-Naphthol-6,8-disulfonic acid Property

Boiling point:

415.13°C (rough estimate)

Density 

1.7421 (rough estimate)

refractive index 

1.6000 (estimate)

form 

solid

pka

-0.33±0.40(Predicted)

color 

Off-white

EPA Substance Registry System

1,3-Naphthalenedisulfonic acid, 7-hydroxy- (118-32-1)

Safety

HS Code 

2904100090

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Warning

Hazard statements

H315Causes skin irritation

H319Causes serious eye irritation

H335May cause respiratory irritation

Precautionary statements

P280Wear protective gloves/protective clothing/eye protection/face protection.

P301+P312IF SWALLOWED: call a POISON CENTER or doctor/physician IF you feel unwell.

2-Naphthol-6,8-disulfonic acid Chemical Properties,Usage,Production

Chemical Properties

2-Hydroxynaphthalene-6,8-disulfonic acid [118-32-1]. (7-hydroxynaphthalene-1,3- disulfonic acid), G acid, C10H8O7S2, Mr 304.3: most salts of 55 are more readily soluble in water than those of R acid, with the notable exception of the potassium salt. Sulfonation with 20 % oleum at 100℃ yields 2-hydroxynaphthalene3,6,8-trisulfonic acid. Diazo coupling takes place in the 1-position, although the reaction is sluggish, as in the case of 2-hydroxynaphthalene8-sulfonic acid.

Uses

The G acid is aminated (Bucherer reaction) to give 2-aminonaphthalene-6,8- disulfonic acid and subjected to caustic fusion at 200℃ to yield 2,8-dihydroxynaphthalene-6-sulfonic acid (a precursor of g acid). It is also used as a coupling component for a wide range of azo colorants, e.g., C.I. Acid Orange 10, C.I. Acid Red 187, and C.I. Food Red 7.

Production Methods

2-Naphthol is added to 98 % sulfuric acid at 40℃. Then, 20 % oleum is added over 6 h and the temperature is allowed to rise to 60℃. The reaction is completed by heating for a further 16 h at 60℃ followed by 15 h at 80℃. After the reaction mixture has been poured into water, potassium chloride is added to the hot solution and the batch is cooled slowly to 35℃ before filtering off the crystalline dipotassium salt of G acid and carefully washing out any residual R salt; the yield is 60 %. In addition, R salt can be recovered from the filtrate in 12 % yield after conversion to its sodium salt.