558 Mr Rohinson, The Adsoi^ption of Acids hy Carhohydrates, 



In every case the solid was completely blackened, and with 

 the stronger solutions the colour of the solution became yellow. 



n was calculated in the same way as before with the following 

 results: 



0-70, 0-62, 0-62, 0-63. 



Mean = 0-64.. 



The corresponding values for k are 



15-3, 16-1, 14-6, 14-6, 14-8. 



Mean = 150. 



Summary of results. 



(1) Carbohydrates adsorb hydrogen chloride and hydrogen 

 bromide with great readiness at the ordinary temperature, but 

 the quantity of acid adsorbed varies greatly with the carbohydrate 

 considered. 



(2) The relative order of adsorption seems to show no relation- 

 ship to the chemical constitution and properties of the various 

 carbohydrates and hence no method has been obtained for cha- 

 racterising them. 



There appears to be no definite connexion between the ad- 

 sorbing power for these acids and the production of bromo or 

 chloromethjdfurfuraldehyde, since starch gives an extremely minute 

 yield of bromomethylfurfuraldehyde, yet it adsorbs most acid. 



The hexaldoses always appear at the bottom of the table. 

 Maltose and lactose differ widely in their powers of adsorption, 

 although they bear a great resemblance in their chemical 

 properties. 



(3) The initial phenomenon agrees with that generally ac- 

 cepted for adsorption, and constant values for n and k have been 

 determined by experiment. 



(4) The process probably consists of a rapid condensation of 

 the acid on the surface of the solid and afterwards it works its way 

 into the interior: this is evidenced by fructose and sucrose and 

 hydrogen bromide, in which case the sugar first becomes pink and 

 eventually black : this black colour may be either due to chemical 

 action or to the formation of an ' adsorption compound ' as in the 

 case of the so-called ' iodide of starch.' 



In conclusion, I wish to tender my best thanks to Dr Fenton 

 for suggesting this research, and for much kind help received 

 during its progress. 



