TRANSACTIONS OF SECTION B. 601 



In any simple chemical change the influence of mass regulates the number of 

 molecular contacts between acting and reacting molecules in unit time ; but if a 

 time factor enters into the molecular reaction, there must be a point beyond which 

 the number of molecular chan(/es cannot increase owing to the restriction of time 

 in the action, and this point will be determined by the relative frequency of 

 molecular contact and the length of the time interval of molecular change. 



There is good reason to believe that during inversion of cane sugar the sugar 

 enters into molecular combination with invertase previous to change, which pre- 

 supposes a time factor of some magnitude. Under these conditions it therefore 

 appears the more probable that this factor limits the effect of mass action in 

 inversion changes as observed iu solutions of ordinary concentration. But if this 

 is so, there must be a point of dilution iu cane sugar solutions when invertase, 

 acting in the dilute solutions, exhibits an order of change in conformity with mass 

 action. The author shows by direct experiment that this point is reached in a 

 solution containing about Iper cent, of cane sugar, so far contirming his conclusion 

 that the time factor of molecular change limits the action of inversion in all but 

 very dilute solutions of cane sugar. 



As the character of the action of fermentation has been shown to resemble 

 that of inversion, it appears very probable that in this enzyme change also the 

 time factor of molecular change limits its action ; and possibly the influence may 

 be evidenced in all enzyme change, and so play an important part in the complex 

 functions of living organisms which depend on enzyme action. 



2. Radium. By Professor W. Maiickwald. 



The Section was then divided into two Departments. 



Department I. 

 The following Report and Papers were read : — 



1. Report on the Relation hetioeen the Absorption Sj^ectra and Chemical 

 Constitution of Organic Substances. — See Reports, p. 208. 



2. On the Chemical and Biological Changes occurring during the Treat- 

 ment of Seicage by the so-called Bacteria Beds. By Professor Letts, 

 D.Sc, Ph.D., and R. F. Blake, F.C.S., F.I.C. 



It is generally assumed that the so-called ' bacteria beds ' act as oxidising 

 agencies, absorbing oxygen from the air during their periods of rest and subse- 

 quently transferring it to the constituents of the sewage when the beds are filled 

 with Ibis latter, the transfer being effected by micro-organisms which have esta* 

 blished themselves on the surface of the material with which the beds are filled. 



It also appears to be generally taken for granted that the micro-organisms 

 mainly concerned in the purification process are the nitrifying organisms. Hence 

 if these views are correct, the effluent from the bacteria beds should contain 

 nitrates and nitrites equivalent in amount to the unoxidised nitrogen which disap- 

 pears during the treatment. But on examining the results obtained by chemists 

 in investigations on sewage purification it will be found that comparatively small 

 amounts of nitrate and nitrite are produced in relation to the unoxidised nitrogen 

 disappearing. 



The following figures are taken (or have been calculated) partly from results 

 given in the Manchester Report of the Rivers Committee, January 22, 1900, 



