INTRODUCTIONEbbinghaus put forward his theory of remote association in 1885. 2 In substance the theory maintains that, when a series of items is learned in a certain serial order, associations are formed not only between adjacent items but also, and at the same time, between items remote in the series. The theory was supported by an experimental investigation which was epoch-making because of its originality. One of the chief innovations introduced by Ebbinghaus was the use of nonsense syllables, which he used exclusively in his investigation. From the point of view of the present study it is particularly to be observed that Ebbinghaus learned his series at a single sitting and to one perfect reproduction. The series were then tested for remote associative tendencies after a lapse of 24 hours.Recently the matter of remote association has been reexamined both theoretically and experimentally by Cason. 8 This writer had his subjects learn a passage of prose by any method which they individually chose, and then recite it 1 The writer wishes to express her indebtedness to Professor Clark L. Hull for suggestions and criticism during the course of the investigation. *H. Ebbinghaus, Memory; a contribution to experimental psychology (trans, by Ruger and Bussenius).
The combined action of bases and acid anhydrides on 7-acylamidocephalosporanic acids, and the action of bases on their esters, set up equilibria in which the corresponding A2-isomers predominate. The isomerisation represents a prototropic shift probably favoured by the sulphur atom in the dihydrothiazine ring. The acetoxy-group in the A2-compounds can be replaced by nucleophiles.Treatment of methyl 3-acetoxymethyl-7~-phenylacetamidoceph-3-em-4-carboxylate 1 [-oxide with a base res u I ts i n d eca rboxy I a t i o n . Attempts to prepare 7 pp he n y I a ceta m i d o ce p h -2 -em -45car boxy I i c acid 1 toxi d e resulted in formation of its A3-isomer and some carbon dioxide.
A polarographic procedure is described for the determination of elemental sulfur in petroleum fractions.Evaluation with synthetic mixtures has shown the method to be accurate to ±2% of the elemental sulfur content in the range of 1 to 100 p.p.m. The method is rapid (about 20 minutes per sample), sensitive, and free from interference from organic sulfides, disulfides, and thiophene.
ANDThe only methods heretofore described for predicting carcinogenic activity have been limited to series of pure aromatic compounds or to high]>-specialized types of petroleum products. After examination of a number of different reactions and properties of polycyclic aromatic compounds, five nonbiological methods have been developed for the prediction of tumor potency of high boiling petroleum products. Each method gave about the same degree of correlation with biological data. These physical-chemical methods are all based upon measurements of certain types of polycyclic aromatic hydrocarbons. The results support the premise t h a t the carcinogenicity is a function qf the concentration of these types of compounds in oils. The methods, therefore, obviate the necessity of isolating or analyzing the actual carcinogenic compounds. The caffeine number method is preferred for routine analytical work. It is based upon a n ultraviolet examination of a n aqueous caffeine extract of the aromatic hydrocarbons. A standard deviation of 8.4 was obtained for the difference between the predicted and the biological tumor potency values of 123 different products. Reproducibility of the caffeine number was better than t h a t of the biological data. Comprehensive analytical data for all five methods are presented for a variety of high boiling petroleum products. These demonstrate t h a t a choice of methods is available, depending upon the particular types of products to be analyzed and the facilities a t hand.
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