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Attention is drawn to the consequences of the finding that adsorbates are in a liquidlike state at temperatures below their bulk freezing point. If the relative pressure is based on the saturation vapor pressure of the undercooled liquid, differences between the N[2] and Kr surface areas and those between the BET and Dubinin-Raduskevich areas become minimal. On application of inappropriate relative pressure values in constructing isotherms, apparent supersaturation may be indicated.

Synopsis A property of water in porous materials is that it freezes at temperatures below 0°C. There is no single freezing temperature for water in soils. As ice is formed the freezing point of the decreasing quantity of unfrozen water falls further below 0°C. Latent heat of fusion is thus involved in temperature changes over a range extending to several degrees below 0°C. The latent heat and specific heat together constitute an apparent specific heat. Apparent specific heats for various silt, clay and organic soils have been measured in a calorimeter. The apparent specific heats generally rise as temperatures approach 0°C, and in a clay soil may be ten times as great at −1°C as at −5°C. The apparent specific heats for a given temperature depend on whether the soil is freezing or thawing, and on various other factors. The precise determination of heat quantities involved in temperature changes in soil in situ is difficult, mainly because of the several factors influencing the freezing of the soil moisture. Une propriété de l'eau dans les corps poreux est qu'elle gèle à des températures inférieures à 0°C. Il n'y a pas de température unique de congélation de l'eau dans le sol. Au fur et à mesure que la glace se forme, le degré de congélation descend au dessous de 0°C. Une chaleur de fusion latente est done en cause lors des changements de température couvrant plusieurs degrés au dessous de 0°C. La chaleur latente et la chaleur spécifique constituent ensemble une chaleur apparente spécifique. Les chaleurs spécifiques apparentes pour des limons, des argiles et des sols organiques divers ont été mesurées dans un calorimètre. D'une manière générale, la chaleur spécifique apparente s'élève lorsque la température s'approche de 0°C, et dans le sol argileux elle peut être dix fois plus grande à −1°C qu'à −5°C. La chaleur spécifique apparente pour une température donnée dépend soit du gel, soit du dégel du sol, et d'autres facteurs divers. La détermination précise des quantités de chaleur en cause lors des channements de température dans le sol, sur place, est difficile, surtout à cause de plusieurs facteurs qui influencent la congélation de l'humidité se trouvant dans le sol.

The system porous glass saturated with respect to water was studied in the temperature range +2 to -40 degrees. Calorimetric measurements with simultaneous observations on length changes revealed that two kinds of transformations took place at different temperatures below the normal melting point of bulk water. The amount of water that did not transform when this system was cooled to about -40 degrees is shown to correspond to approximately three monolayers. The experimental results suggest that the adsorbed water in porous glass even in the middle of the capillaries has a different state from that of bulk water, and it is concluded that the observed depression of the freezing point should be considered in terms of the different structure the adsorbate acquires from that of the bulk state.