SECTIONAL TRANSACTIONS.— B. 



343 



ccUobiose, and maltose admit of this formulation, as also sucrose, raffinose, and 

 inulin. The most satisfactory formula which can be allocated on these principles 

 to sucrose is the following : — 



CHoOH 



I " 



C 



CH 



CHOH 



I 

 CHOH 



Ah— 







A 



IH./OH 



Fructose 

 residue 



CHOH 



I 



CHOH 



CHOH 



I 



CH 



CH2OH 



Glucose 

 residue 



3a. Mr. A. Chaston Chapman, F.R.S., and Dr. H. J. Plenderleith. — 

 An examination of King Tut-ankh-Amen's Cosmetic. 



Friday, August 6. 



4. Joint Discussion with Section A on The Mechanism of Homogeneous 



Chemical Reactions. 



(Mr. C. N. Hinshelwcod outlined the objects of the discussion, which was opened 

 by Prof. Jean Perrin.) 



Monday, August 9. 



5. Discussion on Tautomerism : Prof. C. K. Ingold, F.R.S. ; Prof. 



T. M. LowRY, F.R.S. ; Dr. G. R. Kon ; Dr. R. P. Linstead ; 

 Prof. J. F. Thorpe, F.R.S. 



The scope of tautomerism (reversible isomeric change) is prescribed by reference 

 to the fundamental types of addition reaction of which tautomeric change represents 

 the intramolecular case, the basic condition being the simultaneous presence of 

 mutually suitable dissociable and unsaturated centres. From this standpoint some 

 long known, and some recently investigated, types ot tautomeric change are discussed, 

 with reference to the effect of structural conditions on mobility and equilibrium. 

 Comparisons are drawn between the directive effect of groups in aromatic substitution 

 and their ability to ' direct ' the mobile hydrogen atom into the favoured position. 



The above points are illustrated by reference to such classes of compounds as 

 cyclo Pentadienes, Benzene derivatives, Glutaconic esters, Nitro-compounds, Sugars, 

 Oximea, and Diazo-compounds, and explanations based on the assumption of 

 tautomeric change are given for certain peculiarities of these substances. 



Tuesday, August 10. 



6. Prof. H. ter Meulen. — The use of Hydrogenaiion in Organic Analysis. 



The usual methods for the estimation of sulphur, halogens, nitrogen, arsenic and 

 mercury in organic compounds are based upon destructive oxidations. These 

 determinations can be made quicker by using destructive hydrogenation, which 

 enables us also to estimate oxygen. As a rule the substance that is to be analysed is 

 heated in a quaitz tube through which a current of hydrogen is passed ; in most 

 cases katalysators are used to promote hydrogenation. 



Sulphur is converted into hydrogen sulphide, which is estimated by titration 

 with iodine solutions ; if the amount of sulphur is very low (e.g., in coal-gas and oil). 



