14 Traiimciioiin. » 



of liquid CO2 in the tube, and at -2° under atmospheric pressui'e. Com- 

 position given as CO^SHoO or COoSHaO. 



Other references which were looked up, but from which no further 

 assistance was gained, were : — 



On the Physical Peculinrities of Solutions of Gases in Licpxids, AA'anklvn 

 (Phil. Mag., 1902, 3, 346). 



On the Influence of Pressure on the Electrical Conchictiviti/ of Solutions 

 (Journ. Phys. Chem., 1899, 3, 186). 



Determination of Electrical Conductivity of Solutions ivith Direct-current 

 Instruments (Journ. Phys. Chem., 1901, 5, 536). 



The Lowering of the Freezing -foint of Water produced by Concentrated 

 Solutions of Electrolytes, and the Conductivity/ of such Solutions (Journ. Phys. 

 Chem., 1903, 7, 311). 



Variation of Electric Conductivity at Low Temperatures (Journ. Phys. 

 Chem., 1903, 7, 407). 



Summary. 



From these abstracts the following summary may be made : — 



(1.) Solutions of COo in water, at least mider certain conditions of tem- 

 perature and concentration, contain a certain (comparatively small) number 

 of ions, presumably, by analogy with other weak acids, and from the evi- 

 dence of their chemical behaviour, consisting of H+ and HCO3 , from a 

 molecule of H2CO3. 



(2.) The degree of ionization has been measured by means of the elec- 

 trical conductivity at ordinary temperature and under pressures varying 

 from 1 to 25 atmospheres (Pfeiffer) ; also at temperatures of 12-5° and 

 18°, and concentrations below J^j normal, due to atmospheric pressure 

 (Knox, Walker, and Cormack). 



(3.) A fairly satisfactory dissociation constant, agreeing with Ostwald's 

 dilution law, has been calculated for small concentrations. The degree of 

 ionization under ordinary conditions is very slight, so that HoCO^ is a very 

 weak acid. 



(4.) At 0° and under high pressures a hydrate of COg has been crystal- 

 lized out, stable apparently only under certain corresponding conditions of 

 temperature and pressure. The composition is doubtful — possibly CO^SHoO. 



Grounds of Research. 



It will thus be seen that conductivity-determinations had been made 

 only at the temperatures of 12-5° and 18°, and that high pressures had been 

 employed by only one investigator, Pfeiffer, using from 1 to 25 atmospheres. 

 One statement of Pfeiffer's seemed to call for investigation — namely, that 

 at high pressures the conductivity was constant, being unaffected by 

 change of pressure. This seemed so opposed to the ordinary behaviour of 

 fairly concentrated solutions (a solution of CO2 at ordinary temperatures 

 and under 25 atmospheres pressure being roughly normal) that it was 

 thought worth making a series of conductivity -determinations at 18°. both 

 to settle this point and to check with previous work. 



The conductivity of CO, solutions saturated under various pressures at 

 0° seemed to call for investigation, especially in view of the fact that at 

 this temperature and high pressures a hydrate of CO, had been shown to 

 <>xist, the properties of which, including its composition, had been only 

 vaguely determined (e.g., the discoverer, Wroblewski. stated in one abstract 

 that at 0° the hydrate was formed at 12-3 atmospheres pressure, while in 



