41 



THE SOLUBILITY, RATE OF ABSORPTION AND OF 

 EVOLUTION OF GASES, AS INFLUENCED BY COLLOIDS, 

 WITH SPECIAL REFERENCE TO PHYSIOLOGY AND 

 BREWING. 



By George King, M.Sc, F.I.C. 



Although the conditions governing the equilibrium in the simple 

 gas-Uquid and gas-soUd systems, have received a considerable amount 

 of attention both theoretically^^ and experimentally-* no satisfactory 

 explanation has yet been given of the mechanism of the process-^*. 

 It is not surprising, therefore, to find that comparatively little 

 systematic work has been done on the more intricate problem of gas 

 d'^istribution in colloidal solutions, although it is with such solutions 

 that many of the problems of biology, brewing, botany, sanitation, 

 and agriculture are chiefly concerned. For the purpose of this report 

 the experimental investigation will be considered under : — (1) gas 

 solubiUty in colloidal solutions ; (2) rate of evolution (effervescence) ; 

 (3) rate of solution (aeration). 



I. — Solubility. 



The weU^known Ostwald* co-efficient of solubility gives the ratio 

 of the concentration of the gas in the liquid and gaseous phase 

 C|/Cj = A (solubility) and is an alternative expression of Henry's Law. 

 This law, as Findlay", i^,.", has showTi, is valid for solution of the 

 common gases in water and aqueous solutions of salts and non- 

 electrolytes, at 25° C, and over a pressure range of 250 mm. to 

 1,400 mm. of mercury. Cassutoi", working between one and ten 

 atmospheres, and, more recently, Sander*^, at pressures up to 160 

 atmospheres observed that, at high pressures, the solubility (A) 

 decreased sUghtly with increasmg pressure. 



At such pressures (2,500 lbs. per square inch) the gas concentration 

 in the liquid phase is high, and the observed departure from Henry's 

 Law is presumably closely connected with the compressibility of the 

 concentrated gas solution (c./. Ritzel**)! Biologists often express 

 solubility in terms of Bunsen's coefficient of absorption — the quantity 

 of gas in cubic centimetres at N.T.P. which is absorbed by unit volume 

 of the Uquid at 760 mm. pressure. This coefficient has not proved so 

 satisfactory as the solubility coefi&cient of Ostwald, and Sackur and 

 Stern^" propose to refer the gas absorbed to unit mass of the Uquid. 

 Stern^^ has recently determined the solubility and absorption co- 

 efficients for solutions of carbon-dioxide in ahphatic alcohols, and 

 found that Henry's Law held good to within one per cent., and that 

 the solubihty coefficient was constant over a much wider range of 

 pressures than the modified Bunsen coefficient (c./. also Drucker^^). 



(a) Physiological AsjJect. 



The difficulties which physiologists have encountered in explaining 

 the transport of oxygen and carbon-dioxide by blood have been 



* In a paper published in 1877 (Hufner Wied Ann, 1633) it is suggested that 

 instead of employing Bunsen's eoeflieient, solubilitj'^ should be expressed as " das 

 Verlialtnis des adsorbierenden Fliissigkeits volumens ^m absorbierten gas 

 \'oUinnen " (Drucker). 



