We've been supplying SODIUM SULFIDE FLAKES . The specification for red color is as following:

Na2S :  60%MIN ,

Fe  :  0.15%MAX ,

Na2SO3 : 2.0%MAX,

Na2S2O3 : 2.0%MAX,

Na2CO3 : 5.0%MAX,

WATER INSOLUBLE :  0.4%MAX