Green S is a green synthetic coal tar triarylmethane dye with the molecular formula C₂₇H₂₅N₂O₇S₂Na.

Green S

Names
IUPAC name Sodium 4-[(4-dimethylaminophenyl)-(4-dimethylazaniumylidene-1-cyclohexa-2,5-dienylidene)methyl]-3-hydroxynaphthalene-2,7-disulfonate
Other names Food green S FD&C green 4 acid green 50 lissamine green B wool green S C.I. 44090 E142
Identifiers
CAS Number	3087-16-9 Y
3D model (JSmol)	Interactive image
ChemSpider	82646 Y
ECHA InfoCard	100.019.463
E number	E142 (colours)
PubChem CID	91525
UNII	9B7E8Y9D0X N
CompTox Dashboard (EPA)	DTXSID4046577
InChI InChI=1S/C27H26N2O7S2.Na/c1-28(2)20-9-5-17(6-10-20)25(18-7-11-21(12-8-18)29(3)4)26-23-14-13-22(37(31,32)33)15-19(23)16-24(27(26)30)38(34,35)36;/h5-16H,1-4H3,(H2,31,32,33,34,35,36);/q;+1/p-1 Y Key: WDPIZEKLJKBSOZ-UHFFFAOYSA-M Y InChI=1/C27H26N2O7S2.Na/c1-28(2)20-9-5-17(6-10-20)25(18-7-11-21(12-8-18)29(3)4)26-23-14-13-22(37(31,32)33)15-19(23)16-24(27(26)30)38(34,35)36;/h5-16H,1-4H3,(H2,31,32,33,34,35,36);/q;+1/p-1 Key: WDPIZEKLJKBSOZ-REWHXWOFAE
SMILES [Na+].[O-]S(=O)(=O)c1ccc4c(c1)cc(c(O)c4/C(=C2\C=C/C(=[N+](/C)C)/C=C2)c3ccc(N(C)C)cc3)S([O-])(=O)=O
Properties
Chemical formula	C27H25N2NaO7S2
Molar mass	576.62 g/mol
Melting point	210 °C (410 °F; 483 K) (decomposes)[1]
Hazards
GHS labelling:[2]
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319, H335
Precautionary statements	P261, P305+P351+P338
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

As a food dye, it has E number E142. It can be used in mint sauce, desserts, gravy granules, sweets, ice creams, and tinned peas. Green S is prohibited as a food additive in Canada, United States, Japan, and Norway.^{[citation needed]} It is approved for use as a food additive in the EU^[3] and Australia and New Zealand.^[4]

Green S is a vital dye, meaning it can be used to stain living cells. It is used in ophthalmology, along with fluorescein and rose bengal, to diagnose various disorders of the eye's surface, dry eyes for example.