New York Agbicultubal Experiment Station. 193 



adsorption. 14 Several investigators of formaldehyde disinfection 



"Patten and Waggaman (Absorption by soils. U. S. D. A. Bur. Soils Bui. No. 

 52. 1908) have given a r6sum<5 of the voluminous literature of absorption and 

 adsorption, especially in its relation to soils. Their view of the nature of 

 adsorption appears in the following statement (p. 11): "A special case of 

 absorption has been termed adsorption, which may be defined as the existence 

 of a difference in concentration or density of a film adjacent to a bounding 

 solid and the concentration or density of the mass of the liquid or gas which 

 bathes this solid. Whether this adsorbed film is in a liquid, solid, or gaseous 

 state, or even loosely combined with the solid bounding medium, is not easily 

 determined and has been the subject of much discussion. The change of 

 state from solid to liquid and from liquid to vapor, is very gradual. All the 

 recent physical researches, dealing even with hard, polished 'solid' surfaces, 

 indicate a mobility of parts, an openness of structure, and a high power of 

 retaining foreign material. But the ability of one body to hold another upon 

 its surface is dependent upon the material of which each consists. So we are 

 accustomed to say that adsorption depends upon the chemical constitution of 

 the solid as well as of the substance adsorbed. Another way of stating the 

 same idea is to attribute adsorption to a specific attraction between solid and 

 adsorbed material." 



The great adsorptive capacity of charcoal is well known and often utilized in 

 various arts and industries. " Boxwood charcoal will in this way absorb 

 ninety times its own volume of ammonia, fifty volumes of hydrogen sulphide, 

 or nine volumes of oxygen. * * * The absorbed gases may be removed un- 

 changed by heating the charcoal in a vacuum. The disappearance of these 

 immense quantities of gas into small pieces of charcoal is described as 

 adsorption and is caused by the adhesion of the gases to the very extensive 

 internal surface which charcoal possesses. Solid and liquid bodies are also 

 in many cases taken up by charcoal in a similar fashion. Thus, strychnine 

 may be removed from an aqueous solution by agitation of the latter with char- 

 coal. In the manufacture of whiskey, the fusel oil, which is extremely harmful 

 is in many cases removed by filtration of the diluted spirit through charcoal, 

 before rectification. Organic coloring matters, such as litmus and indigo, 

 belong to the class of bodies thus extracted from solution by charcoal. In 

 the refining of sugar the syrup is boiled with charcoal for the purpose of re- 

 moving a brown resin, in order that the product may be perfectly white. It is, 

 in part, upon this property that we rely, also, in the employment of charcoal 

 filters. The organic materials dissolved in the drinking water undergo adsorp- 

 tion in the charcoal. In this connection, however, it must be remembered 

 that the quantity which a given mass of charcoal may take up is limited, and 

 that careful cleansing is required in order that the efficiency of the filter may 

 be maintained." (Smith, Alexander. Introduction to general inorganic 

 chemistry, p. 476, 1907.) 



In discussing the relation of deleterious chemical agents to the growth of plants 

 Duggar (Plant physiology with special reference to plant production, p. 440. 

 1911) says: " Solid particles such as pure sand, graphite, and filter paper, 

 may reduce toxic action to a considerable extent. True and Oglevee [Bot. 

 Gaz. 39:1-21. 1905] found that twice as much sand as solution may reduce 

 the toxic action of Cu So< for Lupinus albus as much as thirty-two times. The 

 method of reducing toxicity by solid particles is usually denoted adsorption. 

 It is a phenomenon explained upon the hypothesis that many molecules (or 

 ions) of the toxic substance are physically held by the surfaces of the particles 

 of the inert material, and are, for the time, removed from the possibility of 

 chemical action. Another explanation is that the solid substances offer obstacles 

 to the free movement of the solvent particles. Possibly both views are 

 important. Many of the so-called absorptive properties of soils both respect- 

 ing fertilizers and deleterious agents are in reality adsorptive." On this phase 

 of adsorption see, also, Jensen, G. H. Toxic limits and stimulation effects of 

 some salts and poisons on wheat. Bot. Gaz. 43 : 1 1-44. 1907. 



