MR. CUNDALL has recently (Trans., 1891, 59, p. 10'76) published an account of an interesting series of observations on the dissociation which nitrogen peroxide undergoes when dissolved in chloroform. As, according to Van't Hoff, dissolved substances obey the same laws as gases, and the laws of dissociation of binary compounds, such as nitrogen peroxide, are well known for the gaseous state, it is t o be expected that the same laws should hold good for the dissolved peroxide. The law of

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... ion in the gaseous state is expressed by the equation :- where x is the amount of dissociated, and 1z the amount of undissociated peroxide, v the volume of unit mass, and K a coefficient depending chiefly on the temperature, but constant at constant temperature. As Van't Hoff's generalisation is applicable only to dilute solutions, it is necessary to refer to Table I11 of Mr. Cundall's paper (Zoc. cit., p. 1086). In column I1 are given the percentage strengths of solutions, whose reciprocals are equal to l0Ojv of o u r equation. The last column, multiplied by 0.000468 (compare p. 1089), gives the quantity 8. If we denote by c the concentrations (col. 11) of the solutions, and by r the relative amount of NOz (col. IV), we obtain by putting c = lOO/v and z = Om0O0468r.