This paper describes methods of interpolation and exirapolation for smoothing experimentally obtained vapour pressure data of homologous compounds.
Contrary to the customary pro-edures where data of only one component are smoothed and-as far as reference substances of the type as employed in Dühring's rule are applied-always relate to only one reference compound, in the two methods described herein all compounds of a homologous series are considered and-in some cases-correlated with established data of a different homologous series.
In this way, it is possible to smooth systematic deviations which appear in measurements of single components. According to these methods we were able to estimate, by interpolation only, the data of more than 100 compounds for which vapour pressure curves have not been measured so far.
For numerous other compounds it was possible by extrapolation to establish very reliable vapour pressure curves.
Cette communication décrit les méthodes d'interpolation et d'extrapolation des valeurs, obtenues expérimentalement, des pressions de vapeur de composés homologues. Contrairement aux procédés habituels relatifs aux données d'un seul composé et applicables à des substances de référence analogues à celles utilisées dans la règle de Dühring, toujours relative à un seul composé, on considère dans les deux méthodes décrites ici tous les composés d'une série homologue, utilisés tels quels, ou dans certains cas, comparés avec les valeurs bien établies obtenues dans une série homologue distincte.
I1 est ainsi possible de corriger les écarts systématiques obkenus dans les mesures relatives à des com- * Laboratory of Distillation Technique Dr. Hermann Stage in ACV (= Arbeitsgemeinschaft Chemische Verfahrenstechnik), Köln-Niehi, Germany. posants simples. Ces méthodes d'interpolation ont permis la détermination des pressions de vapeur dri plus de 100 composants, pour lesquels jusqu'ici aucune courbe n'a encore été établie.
Par extrapolation, on a pu établir d'une façon sure les courbes de pression de vapeur de nombreux autres composants.
While today we already know more than 3~,ûûû well-defined chemical compounds, there are only 2,000 components for which vapour pressure data have been obtained so far; however, considerable deviations are to be noted even in many of these data (I) *.
Therefore, it is no wonder that efforts have been made for years to discover methods of interpohtion and extrapolation of vapour pressure data which would permit of a correction of experimental errors as well as interpolation or even extrapolation (I (b), 2) when only incomplete data are available. In this connection Dühring's rule (3), the equations of Antoine (4), Rankine (2(f)), Nernst (5), and Thodos (6), and the diagrams of Cox
