"INTRODUCTION Research Project 42 II of the American Petroleum Institute was placed at The Pennsylvania State College for the preparation and study of pure hydrocarbons of high molecular weight. The project is rapidly building a ""bank"" of hydrocarbons of various molecular types@ and is carefully compiling their physical properties. The need for research of this nature is evident. It should permit better conclusions concerning the chemical constitution of lubricating oils@ should clarify the variation of physical properties with chemical structure of hydrocarbons in the lubricating-oil range@ and should supply accurate information required for physical- chemical calculations. Further@ the data thus compiled may well prove particularly valuable in the field of special oils. Reliable methods for the preparation and purification of hydrocarbons in .this molecular~ weight range are being developed. The work of the first 3 years was summarized in the :first 3 papers of this series@'1@2@3 which were presented at the 22nd@ 23rd@ and 24th annual meetings of the American Petroleum Institute. The correlations. of physical properties with chemical structure of 66 pure hydrocarbons of high molecular weight were then reported. The present discussion deals with the continuation of the work@ and 55 additional hydrocarbons of high molecular weight are now reported. They consist of a variety of molecular types: branched. paraffins@ aromatics@ naphthenics@ normal paraffins@ olefins@ and fused-ring compounds. A number of the compounds contain phenyl@ cyclohexyl@ and cyclopentyl groups in the same molecule. Anthracene and phenanthrene derivatives are included. The earlier work on the effect of progressive cyclization to ring structures has been greatly extended@ including the effect of the para-tolyl group@ the 4- methylcyclohexyl group@ the decalyl fused-ring system@ and others. The influence of molecular weight or chain length on physical properties has been studied extensively@ including series of normal paraffins@ branched paraffins@ I-olefins@ mono-pheny1 hydrocarbons@ and mono-cyclohexyl hydrocarbons. Much more work has been completed on the properties of mixtures of these pure high-molecular-weight hydrocarbons@ and the results are very interesting@ The furfural points of all the API 42 hydrocarbons have been determined@ and are reported together with phase diagrams in furfural for 6 of the hydrocarbons. The current synthetic program of Project 42 consists almost exclusively of hydrocarbons. of fused-ring types@ made up of both 5- and 6-membered rings. The development of suitable synthetic methods for such hydrocarbons involves a large amount of research@ and the preparation of 200 g of a pure hydrocarbon of the fused-ring type generally is . very difficult. The experience in the field of heavy hydrocarbons accumulated by Project 42 in the past 6 years is invaluable for this more advanced work. Some of the. special equipment employed?? in the synthetic work and property determinations is shown in Fig. 1 to?? 6. 1 Figures refer to REFERENCE on p. 302."