Table 9: Observed abundance ratios assuming constant abundances.

Source	CN/HCN	CN/NO	CO+/HCO+	SO+/SO
AFGL 2591	1.15	0.74	0.016	0.006
W3 IRS 5	1.80	0.21	0.066	0.007
IRAS 16293	0.05	...	0.001	<0.001
N1333-I2	0.20	0.16	0.002	<0.001
N1333-I4A	0.12	0.03	<0.002	<0.001
L1448-C	0.20	...	<0.002	<0.007
L483	0.75	...	<0.004	...
L723	0.92	...	<0.005	<0.017
SMM4	0.08	...	<0.001	...
L1489	3.85	...	...	...