174 



Prof. B. Moore and Mr. T. A. Webster. 



by Croft Hill* by the use of exceedingly concentrated sugar solutions, and 

 that all such conjugations occur in concentrated solutions. Local concen- 

 tration will have a like effect, and in living cells concentrations on surfaces 

 and interfaces v(rill produce such a result. 



In many of the reactions of inorganic chemistry the differences in totals 

 of chemical energy on the two sides possess a high magnitude at ordinary 

 temperatures, as, for example, in the reaction between hydrogen, oxygen 

 and water. Here the changes in osmotic energy are too insignificant to 

 produce an appreciable effect, and so the reaction runs practically completely 

 to one end or phase. 



But, in the type of reaction with which we are here dealing of conjugation 

 or cleavage where the chemical energy change is relatively small, the osmotic 

 change becomes a powerful factor. 



In the green cell of the living plant the formaldehyde can be condensed 

 on an interface and there conjugate, although general concentration in the 

 cell is kept at a low level. If it be sought to imitate this in a solution of 

 formaldehyde, the concentration must be increased so that the decrease of 

 osmotic pressure may yield energy to supply that required in conjugation, 

 or assist energy supply from without, such as light energy, to increase the 

 potential towards chemical union. 



This is what has been done in the experiments here recorded, in which a 

 reducing substance has been obtained by subjecting comparatively concen- 

 trated formaldehyde solutions to the light of the quartz mercury vapour 

 lamp. 



When six molecules of formaldehyde condense to form one molecule of a 

 hexose, there is only one molecule of dissolved material contributing to keep 

 up the osmotic pressure where there were formerly six, and a corresponding 

 amount of osmotic energy has disappeared as such, and been utilised to yield 

 the slightly higher content of chemical energy which the hexose possesses 

 over that of the formaldehyde which went to form it. The energy so yielded 

 will evidently be proportional to the osmotic pressure at which the form- 

 aldehyde molecules disappear, that is to say, to the concentration of the 

 formaldehyde solution. The osmotic pressure represents the intensity or 

 potential factor of the osmotic energy, and this comes into equilibrium with 

 the intensity factor of the chemical energy, tending bo disrupt hexose into 

 formaldehyde and set energy free. 



This osmotic energy supply is sufficient to yield the amount required, and 

 hence, in this type of reaction, the light plays mainly the part of a catalyst, 



* ' Journ. Chem. Soc.,' vol. 73, p. 634 (1898) ; vol. 83, p. 578 (1903). 



