32 ACTION OF SOLIDS ON DISSOLVED MATTERS. 



oxide of zinc in ammonia; while other solutions, 

 such as that of sea salt, suffer no such change. A 

 bleaching solution of hypochlorite of soda loses 

 entirely its bleaching properties by agitation with 

 charcoal ; and iodine can be removed by the same 

 means from its solution in iodide of potassium. 

 Every one is familiar with the action of finely-di- 

 vided platinum, with that of silver on the deutoxide 

 of hydrogen ; as well as with that of charcoal on 

 dissolved organic matters, colouring matters, &c. ; 

 and freshly-precipitated sulphuret of lead, sulphuret 

 of copper, and hydrate of alumina, resemble the 

 latter in their action. Many organic substances, 

 such as woody fibre and others, act on dissolved 

 matters, such as salts of alumina or of oxide of tin, 

 just as charcoal does ; and we know that the appli- 

 cation of mordants in dyeing, and dyeing itself 

 depend on this very property. The adhesion of the 

 solid colouring matter to the cloth which is dyed 

 with it is the result of a chemical affinity so feeble, 

 that we hardly venture to give the molecular force 

 that name in this case. From a piece of woollen 

 cloth dyed with indigo, the indigo is completely 

 separated, by mere beating, continued for some 

 time, with a wooden hammer, so that the wool is 

 at last left white. 



The surface of the solid body exerts, as these 

 facts prove, a very unequal attraction on the mole- 

 cules, which come in contact with it. 



Researches on capillary attraction have shewn 



