SECTIONAL TRANSACTIONS.— B. 351 



of hydrogen. (4) Slight changes in the solvent can cause reversible 

 aggregation or dissociation (the protein remaining oligodisperse). More 

 drastic, irreversible treatments may cause polydispersity, though others 

 even more drastic may cause no change. The behaviour differs for each 

 protein. 



Such measurements may be used as evidence concerning structure, as a 

 criterion of purity, for controlling preparative procedures, and possibly 

 for diagnosis of disease. 



In collaboration with F. J. Philpot, the sedimentation constant of xanthine 

 oxidase has been determined, vvrith the aid of methylene blue and iodate. 



Afternoon. 

 Excursion to Boots Pure Drug Company, Ltd., Beeston. 



Monday, September 6. 



Joint Symposium with Sections A {q.v.) and I, on Surface action in 

 biology (lo.o). 



Afternoon. 



Excursion to Stanton Iron Works, Ltd. 



Excursion to John Player & Sons, Ltd., Nottingham. 



Tuesday, September 7. 



Symposium on Chemistry of building materials (lo.o). 



Dr. R. E. Stradling, C.B., M.C. — Introduction. 



Dr. F. M. Lea. — Some problems in the study of hydraulic cements 

 (10.10). 



The term ' hydraulic cements ' is usually restricted to those cements 

 which will set and remain permanent under water. In the time available 

 it is necessary to limit the discussion to the most important of the hydraulic 

 cements, Portland cement, together with a brief summary of the properties 

 required in a hydraulic cement. 



The present state of knowledge of the constitution of Portland cement and 

 the relation to the constitution of the properties which are of the most 

 importance in practice, are briefly reviewed and attention drawn to points 

 where knowledge is still lacking. Mention is made of the attack on 

 concrete by ground waters containing sulphate salts and by soft mountain 

 waters. The hydration of Portland cement is considered, leading up to a 

 discussion of the structure of set cement. Certain physical properties of 

 set cements, in particular changes in volume with moisture content and 

 creep, or plastic flow under load, are mentioned and the theory of these 

 discussed. 



Dr. J. S. Dunn. — Calcium sulphate plasters : setting, retarders and 

 accelerators (10.50). 



Only three distinct crystal forms of calcium sulphate have been fully authen- 

 ticated. It is unlikely that the elaborate series postulated by Davies has any 



