PYROGALLOL RED Chemical Properties

Melting point:

133-134 °C(lit.)

Boiling point:

309 °C(lit.)

Density 

1.082 g/mL at 20 °C

vapor density 

4.4 (vs air)

vapor pressure 

10 mm Hg ( 167.7 °C)

refractive index 

n20/D 1.387

storage temp. 

Inert atmosphere,Room Temperature

form 

Liquid

pka

7.86±0.20(Predicted)

color 

Dark brown

Water Solubility 

Soluble in water, ammonium hydroxide (10 mg/ml), and ethanol.

BRN 

363738

CAS DataBase Reference

32638-88-3

EPA Substance Registry System

Spiro[3H-2,1-benzoxathiole-3,9'-[9H]xanthene]-3',4',5',6'-tetrol, 1,1-dioxide (32638-88-3)

Safety Information

Hazard Codes 

Xn,Xi

Risk Statements 

20/21/22-52/53-68-36/37/38

Safety Statements 

36/37-61-24/25-22-36-26

RIDADR 

UN 2811 6.1/PG 3

WGK Germany 

3

RTECS 

UX2800000

F 

8

TSCA 

Yes

HS Code 

2934 99 90

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ACROS
• Language:English Provider:ALFA

PYROGALLOL RED Usage And Synthesis

Chemical Properties

Also know nas pyrogallol and 1,2,3-trihydroxy-benzene,C6H3(OH)3 is white,lustrous crystals that turn gray on exposure to light. It is soluble in water,alcohol,and ether. A solution of pyrogallol acquires a brown color on exposure to air. This absorption of oxygen and change of color take place rapidly when the solution is made alkaline. Derivation is by heating gallic acid in an autoclave with three times its weight of water.
Uses are as a protective colloid in preparation of metallic colloidal solutions, photography, dyes, intermediates, synthetic drugs, medicine (antibacterial), process engraving, laboratory reagent, gas analysis (an oxygen absorber), reducing agent, and antioxidant in lubricating oils.

Chemical Properties

dark brown powder

Uses

The white powdery crystal was made by the superheating of gallic acid. Pyrogallic acid, popularly known as pyro, is one of the earliest developers and its use has spanned three centuries. It was first used in an acid state to physically develop wet collodion negatives. When silver bromide gelatin plates were adopted pyro was used again but in an alkaline state for chemical development. It was used throughout the 20th century and often chosen for the peculiar yellow stain it imparted to gelatin negatives.

Uses

Pyrogallol Red is a complexometric indicator for the metal elements molybdenum and copper. Dyes and metabolites.

Purification Methods

It is recrystallised from aqueous alkaline solution (Na2CO3 or NaOH) by precipitation on acidification, filter it off and dry in a vacuum. [Suk Collect Czech Chem Commun 31 3127 1966, Beilstein 19 H 407, 19 II 417, 19 III/IV 599, 19/10 V 226.]

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