ON THE COMPOSITION OF ZIESITILOLE. 1V.-On the Composikion of Afesititote. (Letter of M. A. CAHOURSto DR. A. W. HOFMANN). In the July number of “The Quarterly Journal of the Chemical Society of London,”* you have communicated the results of some researches on mesitilole which have induced you to assume the expression Cl HI for this compound whose composition Kane had originally repre- sented by the formula C6 H*J which subsequently had been changed into in consequence of my determination of the vapour-density of the body in question. In concluding your memoir you remark that all the facts hitherto observed with regard to mesitilole are in perfect accordance with the new formula the only exception being my determination of its vapour-density ; and you leave it undecided whether the specific gravity of the mesitilole vapour is subject to variations similar to those which have been observed with acetic butyric and valerianic acid or whether the molecule of mesitilole is actually represented by 6 volumes of vapour,-an unusual mode of condensation which would explain the difference exhibited by the properties of this body and those of cumole which like the other hydrocarbons contains 4 volumes of vapour.In preparing the mesitilole for the determination of its vapour-density made at a coinparatively early period I had followed as accurately as possible the directions of Kane who states that this body boils at 135OC. I have since found as you have yourself observed that the boiling point of mesitilole is much higher ;and I have therefore repeated the determinations with a product carefully purified by several rectifications and a final distillation from an-hydrous phosphoric acid.It boiled regularly between 162O and 164O and exhibited exactly the composition of mesitilole. In two determinations made respectively at 74O and 88O higher #. Vol. 11. p. 104. VOL III.-NO* IX. c DR. SHERIDAN MUSPRATT ON THE IDENTITY OF than the boiling point of the hydrocarbon the following numbers were obtained I. XI. Temperature of the air . . . . l7O 200 Yf , vapour. . . . 236O 250° Excess of weight of balloon. . . Capacity of balloon . . . . . 0.396 grm.216 C.C. 0-478grm.275 C.C. Barorrieter . . . . . . . . O"T60 0"*763 Residual air . . . . . . . 0 1 D = 4345 D = 4282 The theoretical vapour-density of mesitilole assuming this body to contain 4 volumes of vapour is 4146. Thus the formula c, H, resulting from your researches on mesitilole and confirmed by Mr. Man le's analysis of nitromesidine,* is in perfect accordance with the specific gravity of the vapour of this compound which ceases moreover to form an exception to the mode of condensation as yet generally observed with carbohydrides. I beg you to communicate these results to the Chemical Society of London.