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The reactions of primary arylamines with aa-diphenyl-p-picrylhydrazyl in carbon tetrachloride have been found to obey the third-order law :Rate of disappearance of hydrazyl = k,[Hydra~yl]~[Aniline] A number of other amines and phenols gave a second-order reaction with the hydrazyl. Alcohols and t-butylamine did not, however, react a t an appreciable rate. The effects of substituents on the reaction with phenols are similar to their effects on reactions in which a carbonium ion is formed adjacent to a phenyl ring. Bulky groups ortho to the phenolic hydroxyl hinder the reaction. The reactions of 9-aminobenzonitrile, mand $-nitroaniline, $-aminobenzophenone, NN-dimethyl-pnitroaniline, and mand p-nitrophenol were greatly accelerated by light, and were then of first order with respect to aa-diphenyl-P-picrylhydrazyl and of zero order with respect to the amine or phenol. BRAUDE, BROOK, and LINSTEAD found that hydrogen transfer took place between the stable free radical aa-diphenyl-p-picrylhydrazyl and a number of quinols, catechols, hydroaromatic compounds, and aromatic amines. They measured the rates of reactions of the hydrazyl with some hydroaromatic compounds in dioxan, found that the reactions obeyed approximately the third-order law (rate = k,[Hydra~yl]~[Donor]), and showed that the energies of activation were between 20 and 35 kcal. per mole. Russell studied the reactions between aa-diphenyl-p-picrylhydrazyl and alkanethiols in benzene and found that the rates of disappearance of the hydrazyl could be expressed as 2k [Hydrazyl][Thiol]. At 6Q0, the values of k varied from 0-23 1. mole-1 min.-l for t-butanethiol to 4.56 for hexanel-thiol and the activation energy was in every case about 15 kcal. per mole. The products of the reactions of thiophenol, butanethiol, ammonia, hydrazine, hydroxylamine, methylamine, n-butylamine, isopropylamine, and diethylamine with aa-diphenyl-@-picrylhydrazyl were investigated and in every case high yields of aa-diphenyl-P-picrylhydrazine were obtained. The reactions between aa-diphenyl-P-picrylhydrazyl and some aromatic secondary amines have also been ~t u d i e d . ~. ~ Homolytic transfers of hydrogen atoms from donors to free radicals are of considerable interest in connexion with termination and transfer processes in chain reactions involving radicals. Autoxidations are important examples of such reactions. The propagation reactions are R* + 0, --t RO,.

An equation which relates the volume term ( V = M / (~L -p g ) ) of unassociated liquids to pressure P and temperature T has been obtained by the combination of (a) 0 . 3 V ( a l / a V )~, , = T,-T for the effect of temperature on V at low (atmospheric) pressure and (b) -V(aP/a V ) T = P, Vx6/ V"P+O + 9( P -p ) for the effect of pressure on volume at constant temperature. In the equations, p is the vapour pressure; p~ the density of the liquid and pe the vapour density. Often pg can be neglected compared with PL a n d p is small compared with the large pressures required to affect the densities of liquids appreciably. There are three constants: T,, P,, which equals 4.455 x 10" N m-2, and V, which can be calculated by rhe addition of atomic values for all the atoms in the molecule and subtraction of a value (6.56 x m3 mol-1) for each bond. When V approximates to Ilt/pL, the molar volume, the equation can be integrated to give the work and heat of isothermal compression. The viscosity of a liquid is related to the work of compression and solubilities in a liquid to the work required to bring the solute to the compressibility of the liquid. Many relationships can be derived and can be used to estimate properties of unassociated liquids.

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