170 TRANSACTIONS^OF SECTION B. 



In the case of heating alone only a slight effect is apparent, but in presence 

 of a substance which can cause an alteration in the arrangement of the mole- 

 cule some profound change occurs. The extent of the rearrangement and 

 consequently the ease with which the change occurs, will depend on several 

 factors, among which the steric effect of constituent groups and the free valency 

 have an important influence. 



It might be expected that, in the series of alkylanilines, the larger groups 

 would show a tendency to be removed before the smaller ones. Comparative 

 experiments with monoalkylanilines indicate that the total amount of change 

 including intramolecular rearrangement, brought about on heating in sealed 

 tubes, does not differ greatly whether the alkyl group is butyl or methyl. It 

 is suggested that the other influences, such as the increasing steric hindrance 

 imposed by the larger alkyl groups, may modify the reaction. 



4. Distillation of Aqueous Solutions of Related Organic Substances. 

 By Joseph Eeilly, M.A., D.Sc, and Wilfred J. Hickinbottom. 



When dilute solutions of organic fatty acids are distilled, it is well known 

 that certain regularities are observed (compare Duclaux, Ann. Inst. Pasteur, 

 1895, 9, 265, 575; Naumann and Miiller, Ber., 1901, 35, 224; Stein, J. pr. Chem., 

 1913, bS, 83). Various forms of distillation constants have been advanced by 

 these authors to express such regularities. These constants may be derived 

 from Nernst's law of distribution. This law may be used as a starting-point 

 for the discussion of the theory of distillation of dilute solutions (Reiliy and 

 Hickinbottom, Sci. Proc. Eoy. Dub. Soc, 1919, 15, 513). For large changes 

 in concentration Nernst's law does not hold exactly, and a method of steam 

 distillation is recommended in which only small changes in concentration occur. 

 By plotting the constants for the normal fatty acids (formic to caprylic acid) 

 against the number of ca.rbon atoms present in the acid, an approximately 

 straight line results, showing an interdependence between molecular constitu- 

 tion and rate of steam distillation. Acids containing a branched carbon chain 

 (as isovaleric) have greater constants than normal acids of the same molecular 

 weight. The experimental evidence at present available shows that for isomeric 

 substances (as for example normal and iso butyric acids), the distillation con- 

 stants are distinct enough to differentiate between the substances. 



The lower saturated monohydric alcohols, phenols, and other substances 

 have been distilled in a current of steam under definite conditions, and results 

 have been obtained showing a relation between molecular complexity and the 

 distillation constants. 



In cases where the constitution of a substance is uncertain, and when it is 

 volatile in steam, a comparison of its distillation constants with those of allied 

 substances may assist in deciding its molecular constitution. 



Within certain limits the distillation constants for formic and acetic acids 

 and the lower satm-ated aliphatic alcohols are subject to variations depending 

 on the concentration. The addition of certain non-volatile substances, such 

 as acids or salts, also causes an alteration in the distillation constants. As the 

 homologous series of saturated fatty acids and alcohols are ascended, the distilla- 

 tion constants increase with the molecular weights, the reverse of what might 

 be expected from a knowledge of the vapour tension of the pure substances. 

 It is considered likely that the tendency for the acids or alcohols to form mole- 

 cular complexes may account for this "behaviour. 



As well as using the method of steam distillation for analysis of fermenta- 

 tion products, and various technical preparations containing the volatile fatty 

 acids, a method has been worked out to detect the presence of butter and of 

 fats of the coconut-oil type in margarine and other products. By determining 

 the distillation constants of the water-soluble volatile acids under definite con- 

 ditions, constants for the fate are obtained which differ considerably in the 

 case of butter fats compared with other fats which have been examined 

 (coconut oil, palm-kernel oil, babassu fat). 



