Fischer3 was the first to describe a definite condensation product from the interaction of glycerol with benzaldehyde and the molecular structure of the cyclic acetal formed was represented as being

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might be reduced by 1000-3000 cal. at room temperature, making it approximately 28,000-30,000 cal. as compared to the above average of -34,200 cal., which also is for room temperature. It is difficult to estimate the accuracy of our results. The most serious source of error is indicated by the presence of considerable amounts of methane among the products of some of the experiments. The corresponding side reaction undoubtedly has displaced equilibrium to some extent. However, in view of the facts that approximately the same endpoint is reached from either side and that our calculated heat of reaction is not unreasonable, we are inclined to believe that our data are not greatly in error. SummaryThe position of equilibrium in the reaction C2H,:~^^~.C2H4 + H2 has been measured at 600, 650 and 700°. Equilibrium was approached from both sides. Some uncertainty exists owing to the simultaneous formation of methane, but the indications are that the equilibrium constants at the three temperatures are 0.0310, 0.082 and 0.20, respectively, partial pressures being expressed in atmospheres.

An experiment carried out with 3 g. of 1,2-benzylidene glycerol, similarly treated with dry hydrogen chloride but without any preliminary heating and allowed to stand for one month at room temperature, yielded 0.45 g. of 1,3-benzylidene glycerol.

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