4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole is an organic compound with the formula SC₂N₃H(NH₂)(N₂H₃). The compound consists of a 1,2,4-triazole heterocycle with three functional groups: amine, thioamide and hydrazyl. X-ray crystallography shows that this molecule is polar but with a C=S double bond. It is prepared by the reaction of hydrazine with thiourea:^[1]

4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole

Names
Preferred IUPAC name 4-Amino-5-hydrazinyl-2,4-dihydro-3H-1,2,4-triazole-3-thione
Other names Purpald; AHMT; 1,2,4-Triazolidin-3-one, 4-amino-5-thioxo-, hydrazone (9CI); 4H-1,2,4-Triazole-3-thiol, 4-amino-5-hydrazino- (6CI,7CI)
Identifiers
CAS Number	1750-12-5
3D model (JSmol)	Interactive image
ChemSpider	2006123
ECHA InfoCard	100.015.578
PubChem CID	2723946
UNII	L49PBF7WZF Y
CompTox Dashboard (EPA)	DTXSID1061944
InChI InChI=1S/C2H6N6S/c3-5-1-6-7-2(9)8(1)4/h3-4H2,(H,5,6)(H,7,9) Key: RDIMQHBOTMWMJA-UHFFFAOYSA-N
SMILES c1(=S)[nH]nc(n1N)NN
Properties
Chemical formula	C2H6N6S
Molar mass	146.17
Appearance	white solid
Density	1.69 g/cm3
Melting point	228 °C (442 °F; 501 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

2 SC(NH₂)₂ + 3 N₂H₄ → SC₂N₃H(NH₂)(N₂H₃) + 4 NH₃ + H₂S

The compound has been used as a reagent for the colorimetric detection of aldehydes.^[2]