Table 4: Abundances in molecular clouds. References: L1689N: SO, SO₂ and H₂S from this work, SiO from Ceccarelli et al. (2000b) and H₂CO from Ceccarelli et al. (2001); L134N: SO and SO₂ abundances from Swade (1989), H₂S from Minh et al. (1989), SiO from Ziurys et al. (1989), from Ohishi et al. (1992); TCM-1: SO abundances from Hirahara et al. (1995) and Pratap et al. (1997), SO₂from Irvine et al. (1983), H₂S from Minh et al. (1989), SiO from Ziurys et al. (1989), from Ohishi & Kaifu (1998).

Cloud	x(SO)	x(SO2)	x(H2S)	x(SiO)	x( )
	(10-9)	(10-9)	(10-9)	(10-12)	(10-8)
L1689N	6-16	0.4	0.3	4	0.04
L134N	0.6-10	0.3-2.5	3	3.6	2
TMC-1	0.3-4	2-6	0.7	2.4	7