1 76 BIO-CHEMICAL JOURNAL 



One is therefore justified in some degree in distinguishing with 

 Schulz ' between the 'essential' and 'accidental' ash-constituents of 

 proteins. The discussion as to the state of combination of these con- 

 stituents in the protein molecule concerns in fact only the former, that 

 part namely which it appears difficult or impossible to remove without 

 destroying the character of the protein itself. 



Now of recent years a considerable amount of research has been 

 undertaken with regard to the nature of the phenomena known by the 

 name of 'absorption' or 'adsorption'. 2 Too much space would be 

 taken up in giving a complete list of this work, and I must content 

 myself with mentioning the names of Van Bemmelen, Biltz, Schmidt, 

 Walker and Appleyard, and Craw. 



The main result of these investigations, so far as concerns us for 

 the present purpose, is the discovery of what we may call the ' Law of 

 Adsorption.' Suppose we have a series of solutions of such a dye as 

 Congo Red, for example, in progressively diminishing concentration, 

 and in each of these we place the same amount of filter-paper, we find 

 that a part of the dye is taken up by the paper and in relatively larger 

 proportion the more dilute the solution. To take some examples from the 

 paper by G. C. Schmidt. 3 



Picric acid and cellulose : 



Concentration of picric acid Amount adsorbed 



0-889 ... o-iii 



0-340 ... 0*095 



Eosin and silk : 



Concentration ofeosin Amount adsorbed 



o - 666 ... 0-84 



0-376 075 



Iodine and carbon : 



Concentration of iodine Amount adsorbed 



O'l6l ... 3'2?5 



0*087 2 '95^ 



1 . Loc. >., p. 1 1 . 



2. Notwithstanding the suggestion of Zsigmondy (Zur Erkenntniss tier Kolloide, Jena, 1905, p. 61, 

 footnote) to make use of the name ' absorption ' in honor of Van Bemmelen, the chief worker on the 

 question who uses this form, I think that, in English at all events, 'adsorption' is less likely to lead to 

 confusion, and ' absorption ' can be still used for phenomena like the solution of gases in water, 



3. Zdtsch, f. Fhynk. Ch(tni(., XV, p. 60. 1894. 



