SECTIONAL TRANSACTIONS.— B. 317 



Afternoon. 

 (a) Visit to works of Messrs. Wood Bros. Glass Co., Barnsley. 



General manufacture of glass and glassware, including the processes involved in 

 making scientific and laboratory glassware. 



Prof. W. E. S. Turner, of the Department of Glass Technology, University of 

 Sheffield, kindly assisted in showing the party round the works and explaining the 

 technical processes. 



(6) Visit to the British Research Association for the Woollen and 

 Worsted Industries, Torridon. 



Mr. A. T. King.— The Chemical Aspect of Wool Research. (See p. 411.) 



Friday, September 2. 



Joint Discussion with Section A on The Structure and Formation of 

 Colloidal Particles. Sir William H. Bragg, K.B.E., F.R.S., Prof. 

 Dr. H. Freundlich, Prof. R. Whytlaw Gray, Dr. F. L. Usher, 

 Mr. B. N. Desai, Mr. J. Ewles. 



Prof. Freundlich. — A distinction between amorphous, crystalline but not orien- 

 tated, and crystalline with orientation, forms of colloidal particles may be made by 

 employment of the X-ray method of analysis. 



The two factors influencing the structure of a colloid particle are the rate of con- 

 densation of the molecules and the rate of their orientation in the crystal lattice 

 under the influence of the crystal forces. While the crystal forces are extremely 

 great in metals, thus giving rise to crystalline colloids of the metals, it has been possible 

 to prepare amorphous silver colloid by rapid condensation and freezing. 



Some indication of the shape of the particles may be obtained by optical methods, 

 and particles which are pear-, spherical-, and rod-shaped, and in the form of lamellar 

 plates of various materials have been examined, as well as the gradual transition 

 from one form to the other with age. 



Prof. R. Whytlaw Geay. — The Process of Coagulation in Smokes and the Structure 

 of the Particles. 



It has been found that these systems are unstable and that the particles are con- 

 tinually coagulating. Consequently, it is difficult to obtain the same degree of dis- 

 persion as in liquid sols. The analogy between these two classes is more apparent 

 than real. Recently a reliable method of following coagulation has been worked 

 out, and the results will be described. 



The larger smoke particles are of microscopic dimensions and it has been found 

 possible to obtain direct information about their structure. 



Dr. F. L. Ushee. — The formation and growth of colloidal particles from molecules 

 are considered in systems from which crystalline structure is absent. The formation 

 of nuclei depends only on the degree of supersaturation and the interfacial tension ; 

 while the growth of the nuclei, in absence of stabilising factors, depends on the relation 

 between the rate of production of the molecules of the disperse phase and the rumber 

 of partially grown particles already present. In stable liquid-liquid systems the 

 particles grow only to a limiting size determined by the electrical conditions of their 

 surface. There is independent evidence of a surface condition which should produce 

 a type of distribution of sizes similar to what is observed. 



Afternoon. 



Visit to the works of Messrs. The Yorkshire Coking and Chemical 

 Co., Ltd., and of Messrs. Hickson & Partners, Ltd., Castleford. 



The Yorkshire Coking and Chemical Co. — Coke oven and by-product recovery 

 plant, including sulphate of ammonia and benzene recovery. Messrs. Hieksoii' — 

 Manufacture of acids and synthesis of dye-intermediates and some dyestuffs from 

 the crude benzol recovered from the coke ovens. The complete manufacture of certain 

 dyestuffs from the coke ovens to the finished product is thus shown. 



