Section III, 1919 [197] Trans. R.S.C- 



The Density of Adsorbing Materials 



By Stuart McLean, M.A. 



Presented by Prof. E. F. Burton, F. R.S.C. 

 (Read May Meeting, 1919) 



The density of adsorbing materials has usually been found by 

 means of a pyknometer as follows: A tube containing the sample 

 under test is heated to expel the adsorbed gas, evacuated and sealed 

 up. The tube is then weighed and the sealed tip broken off under 

 boiling water which rushes in, filling the pores of the material. After 

 cooling, the tube is placed in a pyknometer and the usual procedure 

 followed. 



The following results for coconut charcoal have been obtained by 

 this method: 



Richardson^ 1 • 6 



Miss Homf ray- 1-67 

 1-68 



The object of this experiment was to apply the volumenometer 

 method to determine these densities. The gas used in the volumeno- 

 meter was helium because it is not adsorbed at ordinary room temper- 

 ature. 



A diagram of the apparatus is shown in Fig. 1. 



The sample under test was placed in the tube X. It was heated 

 to a temperature sufficient to expel all the adsorbed gas and the 

 apparatus was evacuated. Pure helium was then admitted through 

 the Travers siphon T. Let V be the volume of the apparatus above 

 the point M. The mercury in the tube MN was raised to this point 

 and the pressure of the gas measured. Let it be Pi. 



The mercury was then lowered to N, increasing the volume from 

 V to V+v. If the resulting pressure is P2, then by Boyle's Law 



p,V = P2(V-fv) 



PoV 



and V= — '— 

 P1-P2 



w ence V may be found, if v is known. 



Thus if Vi, the volume with the tube X empty, and Vo, the free 



. rliime when the material is in it, are determined, the volume of the 



^ Richardson: J. Amer. Chem. Soc, 1917. 



2 liss Homfray: Zs. f. phys. chem. 74, 1910, p 152. 



