February 2-th, 1920.] Proceedings. xxxv. 



applications are : — The clearing of turbid solutions by running 

 them through an adsorbent such as charcoal; it is probably a 

 first step in many dyeing operations and catalytic reactions ; 

 bacteria are removed from water by filtration through sand. 

 McBain and others have shown in some instances that adsorp- 

 tion is followed by solution. 



Sols are suspensions of very small particles in a suitable 

 liquid. The particles have an electrical charge whose sign 

 depends on the method of preparation, and not, as frequently 

 stated, only on the chemical character of the substance. By 

 the X-ray method they are found to be crystalline, although 

 from their optical behaviour they are known to be nearly 

 spherical in shape. Ellis has shown for emulsions that a small 

 reduction in the electrical charge produces precipitation. He 

 has also shown that surface tension has little effect in precipi- 

 tation. Smoluchowski's theory of precipitation was explained. 



The work of Thomson, Harkins and Langmuir on polarised 

 molecules and their consequent effects (1) on the spreading of 

 oil films on liquids, (2) on wetting of solids, and (3) on lubrica- 

 tion, were briefly described ; as also Langmuir 's determination 

 of the length and section of molecules. Sulman's recent paper 

 on mineral separation was mentioned. 



Finally, the necessity for the co-operation of chemist and 

 physicist was insisted on, and support was asked towards the 

 establishment of a Chair of Colloids at Manchester University. 



Special General Meeting, February 27th, 1920. 

 Mr. R. H. Clayton, B.Sc. (Chairman), in the Chair. 

 The proposed Rules of the Section were approved for sub- 

 mission to the Council of the Society for confirmation in 

 accordance with No. 93 of the Articles of Association. 



A copy of the Rules is available for inspection by any 

 member at the Society's House. 



Ordinary Meeting, February 27th, 1920. 

 Mr. R. H. Clayton, B.Sc. (Chairman) , in the Chair. 

 Mr. John Allan, F.C.S., opened a debate on " Engineering 

 as Applied to the Buildings and Plant in Chemical 

 Works." 



The expression " engineering " in the above sense involves 

 knowledge much beyond that of an "astute fitter," and some of 



