1062.    FORESTIER, H., HAASSER, C., AND LONGUET-ESCARD, J.  [Reaction in the Solid State at Low Temperature.  Influence of the State of the Surface and of the Water Vapor Adsorbed.]  Bull. Soc. Chim. France, 1949, D, pp. 146-152; Chem. Abs., vol. 43, 1949, p. 6059.

       Magnetic detection of ferrites is used to study the rate of reaction between solid Fe₂O₃ and oxides of Ni, Pb, and Mg at temperatures low enough for diffusion to be neglected.  For Ni and Pb, reaction can be detected at 200°; for Mg, only above 400°.  Starting mixtures are prepared in 3 ways:  (A) Coprecipitation followed by drying at 100° in vacuo, (B) separate precipitation and drying followed by mixing, (C) separate precipitation and drying at 750° followed by grinding.  The rate and extent of reaction at a given temperature (up to 700°) are (A)>(B)>(C).  The presence of water vapor even in trace amounts considerably increases the rate of reaction for (A) and (B) and has a small effect for (C).  X-ray analyses indicate that with Ni (A) is amorphous but (C) is well-crystallized; with Mg (A) and (B) show Mg(OH)₂, but (C) shows MgO; with Pb (A) is amorphous, but (B) and (C) show the crystalline structure of PbO.  With NiO-Fe₂O₃ mixture (B) at 500°, grinding during the interval of rising temperature results in a slower reaction during the 1^st 1½ hr. at constant temperature, but a faster reaction thereafter.  Compression of the initial NiO-Fe₂O₃ mixture (B) gives a minimum in the % product-pressure curve at about 1,500 kg./cm.³  Mixture (C) shows no minimum.  The data are explained in terms of the number of contact points and the effect of adsorbed water vapor on the surface crystal lattice.

       FOROUD, A. K.  See abs. 162.

       FORRER, R.  See abs. 3639, 3640, 3641, 3642.

       FORREST, H. O.  See abs. 1365.