M1XTUIES OF HYDUOCtll.OItlC AC1I» AND M KT1I VI.ETIIKIS
J P KUENEN.
In 1875 Fuledel ') discovered that methylether (B. 1'. — 23°.5 C.) and hydrochloric acid wlien brought together below zero produce a liquid wliicli boils at 'Z° C.; tliis liquid was not a chemical compoand in the iisual sense: the proportion in which tlie two substances are present in the liquid was not always the sanieand inoreover did not correspond to a siniple inolecular composition (about (i parts of ether against 5 parts of acid). At the sanie time tlie formation ot liquid at temperatures far abovc the boiling-poiut ot the ether and the strong contraction ot' the vapour-inixture above the boiling point which he observed proved that the two substances display a strong mutual affinity. He therefore concluded that the molecules ot the acid and the ether unite to forni a dissociahle molecular coinpound : these doublé molecules occur bot li in the vaponr — hence the abnormally high vapour-density, and especially in the Htjiiid. The latter is a mixture of doublé-molecules and single molecules of the coinponents.
Krom Fiukuel's observations it follows that mixtures ot the substances in question have the com])aratively rare peculiarity ol a maximum in their boiling-points and therefoiv a minimum in their vapourpressures. The object of the investigation described in tliis paper was totrace this niiniinuin up to the critical region and to obtain a complete pressure-tenipcrature diagram for these mixtures. The tlieory ot mixtures develojied by van nr.it \\ aai.s -) makes it very probable that mixtures
') Compt. Rend. Hl p. l,r)2. ' Ki knkn. I'liil. Mag. 41 p.