43 



all pressures, furthermore the hydrogen^' solubility in silver hydrosol 

 was indistinguishable from that in water. Very different is the 

 influence of emulsion colloids on the gas solubility, which is often 

 considerably influenced by the concentration of the disperse phase, 

 and especially is this so mth serum albumen, egg albumen, starch, 

 and dextrin, in which the solubility of carbon-dioxide^^^ nitrous 

 oxide^o, and hydrogen^' is less than in water. Thus the behaviour 

 is comparable with that of the non-electrolj'tes and salt solutions, 

 and in fact provided adsorption and chemical combination do not 

 interfere, collodidal sohitions in general diminish the gas solubiliti/. 

 Thus gelatine, glycogen, ferric hydroxide, ox blood and serum diminish 

 the solubihty of nitrous oxide^® at atmospheric pressure, so also 

 hydrogen in gelatine, nitrogen in blood and serum, and carbon monoxide 

 in serum^^ have a lower solubility than the corresponding gas 'in 

 water. 



For each system at and above a definite pressure there is evidence 

 of adsorption, tliis adsorption effect being greatest for egg and serum 

 albumen and least for gelatine and starch. Very different, however, is 

 the behaviour of a gas which is known to act chemically with the 

 disperse phase in solution. In such systems as carbon-dioxide in 

 methyl orange^', haemoglobin, ox blood, and serum, and carbon- 

 monoxide and oxygen in ox blood and serum^s ii^q g^g solubihty (A) 

 is very considerably increased, and within the range of the pressure 

 investigated (to 1500 mm. of mercury) the solubility decreases with 

 the pressure and the curves show no evidence of adsorption. Judging 

 from solubUity pressure measurements gelatine^*, ferric hydroxide^*, 

 peptone^', and propeptone^'. react chemically with carbon-dioxide 

 and evidence from other soiu*ces confirms this view (c./. Stocks^^, 

 Luther^^). These observations, therefore, support the chemical 

 theory of oxygen and carbonmonoxide absorption by blood and 

 clearly indicate that the absorption of carbon-dioxide must also be 

 considered as in part due to chemical combination. This view of 

 the carbon-dioxide solubility is supported by Hamack^^^ Tissot^", and 

 more recently by Buckmaster^ (c./. also Boycott'). Mention should 

 be made here, however, of the paper by Christiansen^^ and co-workers 

 on the reciprocal solubihty of these gases in blood in which the authors 

 support the adsorption theory. 



(b) Botanical Aspect. 



The question of the assimilation of carbon-dioxide by plants has 

 been shoT^Ti by Willstatter^^ to depend upon the nature of the colloidal 

 chloroph}'!!, and some experiments have shown that, whereas 

 chlorophyll in organic solvents behaves as an electrolyte (c./. 

 Kremann^s) and does not increase the gas solubility, the same 

 chlorophyll in aqueous solution produces an hydrosol which absorbs 

 much more gas " than other colloidal solutions." 



(c) General Application. 



(1) Wolman and Emslow** : — Chlorination of turbid river ^^•ate^. 

 (2) D. Berthelot* and R. Trannoy : — Absorbentjpower of dry and 



