1. Basic Identification Information

Parameter	English Specification/Value
IUPAC Name	2-Methylbenzene-1,4-diamine sulfate (1:1) (also: 1,4-Benzenediamine, 2-methyl-, sulfate)
Common Name(s)	2,5-Diaminotoluene Sulfate; Toluene-2,5-diamine Sulfate; PTDS; para-Toluenediamine Sulfate; C.I. 76043
CAS Registry Number	615-50-9
EC/EINECS Number	210-427-4
Molecular Formula	C₇H₁₂N₂O₄S (or C₇H₁₀N₂·H₂SO₄)
Molecular Weight	220.24 g/mol
Chemical Class	Aromatic diamine sulfate salt; oxidative hair dye primary base; dye intermediate
Related Compound	2,5-Diaminotoluene (TDA, free base, CAS 95-70-5) (parent compound; higher oxidation risk; less stable in formulations)

2. Physicochemical Properties

Property Category	Specific Parameter	Specification/Value
Structural Features	Functional Groups	Two primary amino groups (-NH₂) at C1/C4 positions; methyl group (-CH₃) at C2; sulfate group (-OSO₃H) as counterion (protonates amino groups for stability)
Physical Appearance	State & Color	White to pale yellow crystalline powder; stable color (no darkening on exposure to air compared to free base); faint amine-like odor
	Melting Point	>300 °C (decomposes without melting)
	Density (25 °C)	1.48 g/cm³ (crystalline form)
Solubility	Polar Solvents	Soluble in water (5.03 g/L at 20 °C); very soluble in dilute acids (forms more soluble salts); moderately soluble in ethanol (1–10 g/L)