Table 4: Calculated column densities (cm^-2) in Persei for undetected species.

Species	Diffuse Phase	Dense Phase	Total
D	3.6(15)	3.0(14)	3.9(15)
Si	4.0(13)	9.5(12)	4.9(13)
H+	9.6(16)	1.8(12)	9.6(16)
D+	2.5(11)	3.0(06)	2.5(11)
H2+	1.4(12)	1.3(08)	1.4(12)
H2D+	6.5(09)	1.2(06)	6.5(09)
OH+	7.6(11)	3.1(06)	7.6(11)
H2O+	5.5(11)	2.9(06)	5.5(11)
H3O+	5.2(11)	4.5(06)	5.2(11)