Neville’s Acid/NEVILLE & WINTHER`S ACID/N.W.ACID/1-Naphthol-4-sulfonic acid （CAS NO: 84-87-7 ）

Properties

♦  Basic Identifiers

Its molecular formula is C₁₀H₈O₄S, with a molecular weight of 224.23 g/mol . Common synonyms include 4-hydroxy-1-naphthalenesulfonic acid

♦ Appearance and Form:

At room temperature, it presents as a white to yellow or off-white solid . It is commercially available in different physical forms, such as a dry

powder or a wet paste, to suit various  industrial    handling and processing needs

 

♦  Solubility and Acidity:

It is characterized as easily soluble in water . Its solutions are strongly acidic, typically exhibiting a pH value of less than 2

 

♦ Thermal Properties:

The compound has a melting point of 170°C, at which it decomposes, and a predicted boiling point of 427°C

 

♦  Density and Partition Coefficient:

It has a density of approximately 1.55 g/cm³ . Its LogP value, a measure of its hydrophilicity, varies in different databases (e.g., -0.44 to 2.87), reflecting a balance that is important for its role in dye synthesis

♦  Commercial Specifications & Purity

Industrial grades are often sold at a minimum purity of 65% . Key impurities are strictly monitored and include residual naphthionic acid (typically <0.3%) and SO₂ content (<0.3%) . For specialized applications like reference standards, high-purity material (>99%) can be obtained through advanced purification techniques such as high-speed counter-current chromatography .

 

Applications

♦  Azo Dye Intermediate:

Its main application is as a coupling component in the synthesis of a wide range of azo dyes . These dyes are essential for coloring various materials.

♦ Direct Dyes:

It is used to produce dyes like Direct Copper Blue BR and Direct Violet RB for cellulose fibers

♦ Acid Dyes

It serves as an intermediate for dyes such as Acid Red B, used for wool and silk

♦  Mordant Dyes: 

It is also a precursor for dyes like Acid Mordant Bordeaux B

♦  Food Colorants:

It is a key intermediate in the manufacture of FD&C Red No. 4 (Ponceau SX), a color additive certified for specific food and drug applications in some countries

♦ Other Applications：

Beyond bulk dye manufacturing, high-purity Neville’s Acid is crucial as a reference standard in analytical chemistry for developing testing methods . It is also used in biochemical research as a model compound or for synthesizing other complex organic molecules .

Process

♦ Addition:

Sodium 1-naphthylamine-4-sulfonate undergoes a 1,4-addition reaction with sodium bisulfite in the presence of hydrochloric acid.

 

♦  Hydrolysis:

The adduct is hydrolyzed under alkaline conditions (e.g., with caustic soda), replacing the amino group with a hydroxyl group to form disodium 1-naphthol-4-sulfonate, while releasing ammonia gas.

 

♦  Acid Precipitation:

Hydrochloric acid is added to the hydrolysate for acidification. The target product then crystallizes out in its free acid form.

 

 

Inspection

♦ Inspection process

1. Incoming inspection: The main raw materials,are inspected for their content, appearance

and other main properties.

2. Feeding inspection: the principle of raw material feeding is first-in-first-out, and the appearance

of the main raw materials is randomly inspected according to whether there is a big change in the

storage conditions before feeding.

3. Batch sampling in the production process: During the production process, the main indexes of

each batch of products: content and acid value will be examined three times in different time periods.

      4. Storage Inspection: Each batch (4tons) is inspected before storage

 

♦ Inspection Method

Physical Appearance: Visual inspection

Purity Analysis:Gas chromatography (GC)

Water Content:Moisture analyzers

Density:Density meter

Marking, packaging, shipping and storage

♦ Marking

Each batch of products should be accompanied by a certificate of conformity, including: the name of the

manufacturer, the name of the product, the production batch number, the net weight per barrel, the quality

level and the implementation of the standard number.weight, quality grade and implementation standard

number.

♦ Packing

Packed in clean and dry plastic drums or Kraft bags, net weight are 25kg or 40kg compressed and  sealed after each batch.

♦ Transportation

This product is packed in plastic drums, during transportation and loading/unloading, it should be carefully

and gently put down, and prevent from impact.

♦ Storage

The storage place should be cool, dry and ventilated. Do fireproof and rainproof.