238 Journal of the Asiatic Society of Bengal [May, 1907. 



This is of course Henry's Law for tlie solution of a gas in a 

 liquid. It is possible to put forward several different suggestions 

 as to wLv the eouilibrium curves are losraritliniic at the lower tem- 



Ly the equil 

 peratures, but none of them appear to be adequate. 



Though in the case of a substance such as charcoal, which 

 may be considered as homogeneous, the simple exponential law 

 holds, it is not to be expected that it will be directly applicable to 

 such systems as cotton, wool, etc., in contact with water vapour. 

 Such materials as vegetable fibres cannot be considered as homo- 

 geneous, and are probably built up of several amorphous sub- 

 stances. 



In the course of last summer I carried out some experiments- 

 on tlie o.hsorption of water vapour by cotton and wool at 0°C., and 

 the results, which have been submitted to the Royal Society, are 

 represented by the curves in Fig, 2. It will be observed that 

 they are of the same form as those representing the equilibrium 

 betv^een carbon dioxide and charcoal, but they are not represented 

 equally well by the simple exponential formula. The equilibrium 

 curve for cotton at 26°C- was determined for low pressures only,, 

 and it will be observed that it is more nearly linear than the curve 

 for O^C. On extrapolation we find that while at 0° cotton can 

 take up 8 per cent, of its weight without becoming saturated, at 

 26^ it can only take up about 4 per cent, of moisture. 



It will be observed that wool is more susceptible to changes of 

 humidity than is cotton, and herein lies the advantage of employ- 

 ing it as a material for clothing. A quantitative study of the be- 

 haviour of fibres, timbers, cork, etc., towards water, will indicate 

 their suitability for many purposes to which they are applied. A 

 considerable amount of discussion has recently arisen over the 

 qiiestion of moisture in jute, and perhaps my results may be of 

 assistance to those who are engaged in the investigation of the 

 problem. 



The absorption of water by crystalline materials, such as the 

 components of the soil, is in all probability of a totally different 

 character. The greater part of the water present in the soil is 

 probably present as *free water,' and the pressure of the vapour . 

 in contact with it is probably only lower than the saturation pres- 

 sure in proportion to the quantity of soluble matter present. 

 This problem awaits solution. 



The ahsorpfion of snhstances from solution hy solids and amorphous 



substances. 



The distribution of soluble djes, salts, etc., between the bath 

 and such amorphous materials as plant fibres, follows the logar- 

 ithmic law of distribution, and this may be taken as evidence that 

 neutral dyes are present in the fibre in a state of solution. This 

 is sufficient to explain why cotton does not dye with indigo as 

 effectively as wpol*; it is probably an inferior solvent for indigo 

 white, just as it is an inferior solvent for water (see Fig. 2). 

 Data with regard to absorption will be found in the following 



