Mr Brown on the Mucilage of the Fucu 411 



Its real characters are those of mucilage, procured from 

 marsh-mallow roots and the pericarp of lintseeds. 



The acetate of lead, and the well-known precipitants of mu- 

 cilage, throw down a white curdy mass from a solution of the 

 principle in question. 



More than this, I have ascertained that the following new 

 properties are common to the mucilaginous matters procured 

 from the fuci and the sources just referred to. 



When to a solution of either mucilage, a little cyanide of 

 iron and potassium is added, before the dropping in of sulphate 

 of zinc, there falls a curdy compound of the cyanide of zinc 

 with the mucilage. In a similar manner other insoluble cyan- 

 ides may be thrown down with it. 



By changing the circumstances, in a manner which will be 

 evident to the chemist, we may precipitate similar curdy com- 

 binations of mucilage with the insoluble chlorides and iodides. 



If what is called hydro- sulphate of ammonia be mixed with 

 a solution of mucilage, whether obtained from the fuci or the 

 other sources, and there be added nitrate of silver, there is pre- 

 .cipitated a black compound of the mucilage with sulphur^t of 

 silver. A similar result may be predicated of all the insoluble 

 sulphurets. In fine, by a skilful adaptation of circumstances^ 

 mucilage may be made to combine with all the insoluble bi- 

 elementary electro-positives, and this unusually general cha- 

 racter belongs to tangle-ware as well as marsh-mallow mucilage. 

 If other communities of feature be necessary for their identifi- 

 cation, I may add, that a solution of that from the fuci yields, 

 with borax, a jelly which, while drying spontaneously, con- 

 tracts with such force as to crush the glass vessel which con- 

 tains it, and that, by long boiling with sulphuric acid, it is 

 changed into a substance endowed with the qualities of gum- 

 arabic. 



I may here remark, that there exist essential differences be- 

 tween gum-ai-abic and mucilage. A solution of gum-arabic 

 (which erroneously retains the name of mucilage in the Phar- 

 macopeias of the Colleges) quickly acidifies and moulds, whilst 

 that of mucilage never does so. 



Professor John states that the Fucus vesictdoms contains 



Dd2 



