324 SECTIONAL TRANSACTIONS— B. 



the Tees is toxic to Neoniysis vulgaris and Crangon vulgaris, but not to 

 Gammartis and Corophium. 



Experiments on Eurytemora hirundoides and on the Dog Crab {Carcinus 

 nieenas), both of which occur in the most polluted part of the Tees, have 

 shown these organisms to be of relatively high resistance to cyanide. The 

 lack of certain animals in the estuary as food for fish is of secondary import- 

 ance, as the fish are more susceptible than invertebrates to poisons. 



Tuesday, September 6. 



Prof. C. H. Desch, F.R.S. — Re-arrangements in the solid state. 



Systems in which a series of solid solutions, stable at high temperatures, 

 resolves itself into two or more phases on cooling are of frequent occurrence. 

 In most instances the change takes the form of the separation of a new 

 phase from solution in the same manner as the crystallisation of a salt from 

 water. A solubility curve may be drawn, and eutectoid structures, similar 

 to the eutectics formed from liquid solutions, are produced. The iron- 

 carbon and iron-nickel systems are familiar examples. In recent years 

 another type of re-arrangement has become known, and is typified by the 

 gold-copper alloys. A solid solution, homogeneous at high temperatures, 

 and having the solute atoms statistically distributed throughout its lattice, 

 assumes a new arrangement on cooling through a certain point, the solute 

 atoms taking up regular positions and so forming a super-lattice. This 

 change is reversed on heating. The number of such systems may be con- 

 siderable. The nature of the re-arrangement and its effect on the structure 

 of the solids are discussed. 



Discussion on Liquid mixtures CProf. Irvine Masson ; Prof. J. 

 Kendall, F.R.S. ; Dr. N. V. Sidgwick, F.R.S. ; Dr. J. A. V. 

 Butler) : — 



Prof. Irvine Masson. — Introduction ; Phenomena in liquid mixtures. 



Prof. J. Kendall, F.R.S. — Compound formation in liquid mixtures. 



Compounds existent in liquid mixtures may be divided into two types — 

 addition compounds and substitution compounds. In the first type, of which 

 acetic acid-aniline is an example, there is a definite increase in molecular 

 complexity, and the physical properties (e.g. viscosity, specific conductivity) 

 diverge considerably from the mean of the components. In the second type, 

 of which phenol-cresol is an example, there is no increase in molecular 

 complexity and the physical property-composition curves are more nearly 

 linear. 



The main factor inducing compounds of the first type is diversity in 

 electrochemical character of the radicals of the components, the extent of 

 compound formation in solution increasing with such diversity. The main 

 factor inducing compounds of the second type is similarity in the radicals 

 of the components, part of an associated molecule being replaced by 

 essentially equivalent groups. 



A detailed examination of the two ternary systems ethyl acetate-water- 

 alcohol and ether-water-alcohol has been made, and the results obtained 

 have been analysed in the light of the above generalisations. 



