C2H2 data from Tickner & Lossing (1951).
 T(K)     P(bar)
145.15   1.33e-02
140.25   6.67e-03
134.15   2.67e-03
129.65   1.33e-03
125.75   6.67e-04
120.75   2.67e-04
117.25   1.33e-04
114.05   6.67e-05
109.75   2.67e-05
