SECTIONAL TRANSACTIONS— A. 309 



Tuesday, September 6, 



Joint Discussion with Section G (Engineering) on The theoretical and 

 practical aspects of the control of humidity in industrial processes. 

 (Representatives of the woollen, timber, photographic and cocoa 

 industries participated, together with manufacturers of humidity 

 control and measuring apparatus.) (Dr. Ezer Griffiths, F.R.S., 

 Mr. J. H. AwBERY and Mr. R. W. Powell ; Mr. J. Frith and 

 Mr. F. Buckingham ; Dr. S. G. Barker and Mr. M. C. Marsh ; 

 Dr. S. F. Barclay ; Prof. S. Lees ; and others) : — 



Dr. Ezer Griffiths, F.R.S., Mr. J. H. Awbery and Mr. R. W. 

 Powell. — The evaporation of water in an air- stream. 



Mr. J. Frith and Mr. F. Buckingham. — The theory of drying. 



(i) The problem. Methods of drying. The application of Dalton's 

 Laws. Relative humidity. 



(2) The wet and dry bulb thermometer. Interpretation of its readings. 

 The constancy of the wet bulb reading during evaporation and the suggestion 

 that this reading is a measure of the total heat of a given mass of any mixture 

 of air and water vapour. Discussion of the accuracy of the simplified 

 expression : 



p' ~p=K{T - T'). 



(3) The proof of the total heat theory. The calibration of a wet bulb 

 thermometer as an instrument to measure total heat per pound of any 

 mixture of air and water vapour. Comparison of the above calibration with 

 that calculated from the latest experimental figures of Awbery and Griffiths. 

 Calculation of hygrometric tables from the total heat theory and comparison 

 with Awbery and Griffiths' results. Actual value of the constant K in the 

 simplified expression above. 



(4) The application of all the above to the practical solution of drying 

 problems. 



Dr. S. G. Barker and Mr. M. C. Marsh. — Controlled humidity in 

 woollen and worsted mills. 



Prof. S. Lees. — The drying of air, particularly by the silica gel process. 



Dr. F. J. W. Whipple. — Continuous records of vapour-pressure. 



Mr. B. G. McLellan. — The significance of humidity conditions on the 

 making and marketing of foodstuff s . 



Mr. R. S. Whipple. — The instrument-maker and the control and 

 measurement of humidity. 



Dr. A. Ferguson. — Evaporation from plane and spherical surfaces. 



Mr. F. Short. — Humidity -measuring instruments. 



Mr. R. G. Bateson. — The control of humidity. 



Dr. F. T. Peirce. — The influence of moisture on cotton technology. 



