.In this paper it is demonstrated that the rare-earth metals: cerium, lanthanum. neodymium and didymium all show a series of at least four reversible allotropic changes; the different phases are discerned as (I-. /I-, yand &states of these metals.From the study of the specific heat, the thermal expansion, the electrical resistance and the thermoelectrical behaviour in their dependence on the temperature, it becomes obvious that the inner state of all these metals is a t each temperature a highly complicated one, it being characterized by the simultaneous co-existence of several of these modifications. As the transformations between these modifications occur very slowly, in general the instantaneous inner state of these metals is not one of perfect equilibrium and, therefore, depends ac each temperature to a high degree on the mode and duration of their preliminary thermal treatment, as well a s on the time during which the samples, after treatment, are preserved and again examined.The transition-temperatures are, in all cases, situated between -170" and about 720" C; the special character of the accompanying retardationphenomena is different in each case. More particularly. neodymium manifests most remarkab:e cyclic effects, a peculiar internal thermo-electrical force and an abnormal thermal expansion within the limits of a transitioninterval, -all indicating the physical inhomogenity of the metal investigated. 2.3. j 1. In the present paper we communicate the final results obtained in an investigation ccncerning the thermal and electrical properties of the metals cerium, lanthanum and neodymium and of didymium, -the binary mixture of neodymium and praseodymium, found in nature. The properties of these metals here considered are: the specific heat, the electrical resistance, the thermoelectrical behaviour and the thermal expansion in their dependence on the temperature.T h e results obtained are of particular interest: not only because of LVlI 3&

Nous attendant a la formation d'un acide disulfontque, nous avons etudie la reaction du 2.3~dimtHhylbutadiene avec le sulfite acide d' ammonium.La reaction a donne un produit bien cristallise, fondant a 135 0 • qui cependant n'etait pas le sel ammoniacal d'un acide sulfonique, mais un compose neutre de soufre, exempt d'azote et non-hydrolysable.Les determinations du poids moleculaire selon deux methodes ont donne environ 150, tandis que la reaction avec Ie brome a accuse la presence d'une double liaison, Enfin l'analyse a conduit a la formule C 6H 1002S. Un compose neutre de soufre peut etre un thioether, un sulfoxyde ou une sulfone. Comparant la formule trouvee a celle du dimethyl butadiene C 6H IO on doit condure a la formation d'une sulfone par addition de S02'En admettant une addition au systeme conjuque, on parvient au schema reactionnel suivant: