72.   ARMBRUSTER, M. H.  Solubility of Hydrogen at Low Pressure in Iron, Nickel and Certain Steels at 400°-600°.  Jour. Am. Chem. Soc., vol. 65, 1943, pp. 1043-1054; Chem. Abs., vol. 37, 1943, p. 4283.

               The solubility (s, in micromoles per 100 gm.) of H₂ was measured over a range of pressure (p) from 0.001 to 1.5 mm. in carefully pretreated samples of a-Fe (initially carbonyl Fe), Ni, and certain steels at 400°, 500°, 600° and at pressures up to 350 mm. in the Fe at 600°.  The results are reproducible in all cases are in accord at each temperature, within the precision of the measurements, with the linear relation s=ap.^1/2.  The measurements on Fe and Ni at all 3 temperatures are accurately reproduced by the respective equations (T is absolute temperature): log (s/p^1/2)=-1454/T+1.946 and log (s/p^1/2)=-645/T+1.732.  A similar equation holds for each of the several steels, which fall into 3 groups, according as each is (1) ferritic with low alloy content, (2) ferritic with high alloy content, (3) austenitic.  The solubility in the low alloy steels differs little from that in pure Fe, but the small individual differences for different compositions are quite reproducible.  A method is presented of calculating the amount of residual H, independent of any blank measurement to determine its effective volume (or effective pressure), from a suitable plot of the actual measurements; the result, so calculated, is identical with that obtained through the use of a blank with A in the presence of the sample.  Comparison by extrapolation of the new results with data in the literature shows a general accord. particularly at temperatures of 600° and higher; at lower temperatures the values obtained in this investigation are, because of their consistency with the foregoing linear relations, believed to be of superior accuracy.  After the pretreatments, reproducible equilibrium was obtained within a few min., except in the case of the 13%-Cr steel in which the unreducible, barely visible, oxide film slowed down the rate.