From Big Medical Encyclopedia

ABSORPTION (absorptio; lat. ab — from, from and sorbeo — I absorb) in chemistry — absorption of gas or solute liquid or a solid. The absorbed substance (absorbtiv, or absorbate) is dissolved in an absorber (absorbent), being evenly distributed on all its volume. Thus, absorption is similar to dissolution, than differs from adsorptions (see) — process of absorption of gases or solutes a surface of an absorber.

Special value for medicine has And. gases liquids since this process is the cornerstone of gas exchange between an organism and Wednesday (see. Gas exchange ). Quantitative measure And. gases the coefficient serves in liquids And. (solubility coefficient). Several ways of expression of coefficient are known And., from which the following is most often used.

Coefficient of absorption of Bunsen (a) — the volume of the gas (given to normal conditions — t ° 0 ° and 1 atm of pressure), dissolved in unit volume of liquid at this temperature and partial pressure of gas, equal 1 atm.

Coefficient of absorption of Van-Slayka (α0) — the volume of gas (in cm3) specified to normal conditions, dissolved in 1 ml of liquid at this temperature and partial pressure of gas, equal 1 atm.

Coefficient of absorption of Ostvald (β) — the volume of gas measured in experimental conditions (without reduction to normal conditions), dissolved in unit volume of liquid.

In the table coefficients of absorption of Bunsen (as the most common) for some gases having physiological value in water and a blood plasma are given at t ° 38 °.

Size A. gases liquids depends by nature gas and liquid, pressure of gas and temperature. So, according to Henry's law concentration (C) the gas dissolved in liquid kr where k — coefficient of proportionality is proportional to pressure (R) of gas over liquid, or With =. If With it is expressed in volume of the gas given to normal conditions, which is dissolved in unit volume of liquid, and pressure P — in the atmospheres, then to it is equal to coefficient of absorption of Bunsen.

Henry's law is applicable for slightly soluble gases. And. gas decreases with temperature increase (the way of venting from liquids by boiling is based on it idle times).

At And. to mix of gases degree of solubility of each gas in this liquid is proportional to its partial pressure over solution (Dalton's law). Change of solubility of gases with change of pressure has essential value in a pathogeny of gas embolisms (see) and a caisson disease (see. Compressed-air disease ).

In solutions of salts A. it is less gases, than in pure water. I. M. Sechenov (1892) established the following ratio characterizing influence of salts on solubility of gases in aqueous solutions:

lgn(0/n1) = kC

where n0 and n — solubility of gas in water and in solution of salt with concentration With mol/l respectively, k coefficient of proportionality size to-rogo is defined by the nature of salt.

See also Diffusion , Sorption .

Bibliography: Brodsky A. N. Physical chemistry, t. 2, page 497, M. — L, 1948; The Macintosh P., Cars At. and Epstein of X. Physics for anesthesiologists, the lane with English, M., 1962.

V. P. Mishin