2.Insoluble metal sulfides PbS Bi2S3 CuS CdS Sb2S3 SnS2 As2S3 HgS Their colors are often used for qualitative analysis2. Insoluble metal sulfides PbS Bi2S3 CuS CdS Sb2S3 SnS2 As2S3 HgS Their colors are often used for qualitative analysis