Table 1. Comparative ionic permeabilities via chord conductances at −180 mV.

Test Ion	Conc. (mM)	Figure no.	pHo	Size (ϕ)	Im pA	Gm pS	aP/107 cm s−1
Cl−	183	4	7.5	1.0	26.7	148	1.13
Br−	175b	4	7.5	0.77	41.6	231	2.29
I−	175	4	7.5	0.81	44.1	245	2.30
SCN−	175c	7	7.5	1.0	35.2	196	1.49
NO3−	175	–	7.5	1.0	45.8	254	1.94
SCN−	30b	7	7.5	1.0	55.6	309	13.6
NO3−	30	–	7.5	1.0	39.7	220	9.72
NO2−	30d	5	7.5	1.0	52.6	416	12.9
Cl−	183	4	5.5	1.0	105.0	583	4.45
Br−	175b	4	5.5	0.77	85.6	476	4.70
I−	175	4	5.5	0.81	90.7	504	4.74
SCN−	175c	7	5.5	1.0	49.9	277	2.11
NO3−	175	–	5.5	1.0	45.8	254	1.94
Formate	175	–	5.5	1.0	15.9	88.4	0.671
Gluconate	175	–	5.5	1.0	8.3	46.2	0.351
Acetate	175	–	5.5	1.0	4.6	25.5	0.194
H2PO4−	170e	–	5.5	1.0	1.2	6.9	0.054
Cl−	30b	2	5.5	1.27	30.3	168	5.83
SCN−	30	7	5.5	1.0	42.7	237	10.5
NO3−	30	–	5.5	1.0	39.7	220	9.72
NO2−	30d	5	5.5	1.0	60.2	730	14.7

^aFormally, G_m] ₋₁₈₀=−I_m]₋₁₈₀/0.18, and the relevant permeability (e.g., for Cl⁻) is P_Cl=(RT/2F²)×(G_m]₋₁₈₀)/[Cl⁻]_i, where the factor 2 represents the standard surface area, 2×10⁻⁶ cm². P_Cl is normalized (÷ ϕ) for cell surface areas (see values in figure legends)

^bAll buffer solutions contained 8.3 mM residual Cl⁻, which was included in the total concentration used to calculate permeabilities, except for SCN⁻ and NO₃⁻. See legend to Fig. 4

^cFor thiocyanate and nitrate, only their actual concentrations (175 and 30 mM) were used, assuming simultaneous blockade of chloride. See esp. legend to Fig. 7

^dCalculations done as if NO₂⁻ currents added to Cl⁻ currents appropriate for 153 mM. This would be the superchloride behavior suggested in the text description of Fig. 5

^eCorrected from 175 mM, due to second dissociation at pK_a=7.2