Table 9.

Sensitivity of $c_0^2$ to impurities

Impurity	M (g/mol)	γ0	$\frac{1}{c_0^2}\frac{d(c_0^2)}{dx}$
			in He	in Ar
H2	2	1.4	0.23	0.68
He	4	5/3		0.9
H2O	18	1.32	−3.93	0.12
Ne	20	5/3	−4.0	0.5
N2	28	1.4	−6.27	0.03
O2	32	1.4	−7.3	−0.07
Ar	40	5/3	−9.0
CO2	44	1.4	−10.3	−0.37
Kr	84	5/3	−20.0	−1.1
Xe	131	5/3	−31.8	−2.3
Hg	201	5/3	−49.0	−4.0