278 Mr. C. Tomlinson on the Action of Solid Bodies 



Catharization is the act of cleaning the surface of bodies fron. 

 all alien matter ; and the substance is said to be catharized when 

 its surface is so cleared. 



The methods of doing this are various. The action of flame 

 or of strong sulphuric or nitric acid, or of alkaline solutions is 

 efficacious according to the nature of the surface. In some cases 

 steeping the solids in water during several days may suffice ; in 

 others boiling them in acid or alkaline solutions, or rubbing 

 them between corks or platinum-foil while immersed in the 

 strongest commercial oil of vitriol, or washing them with alcohol 

 or ether may be necessary, but always finishing with a co- 

 pious rinsing in a stream of water. Should any one of these 

 methods fail in any particular instance, another may be resorted 

 to. For example, a short cylinder of phosphorus cut out of a 

 stick that had been previously scraped was attached loopwise to 

 a platinum wire, and so lowered into a test-tube (cleaned by the 

 action of strong sulphuric acid and copious rinsing) containing 

 soda-water*. Not a single bubble of gas appeared on the walls 

 of the tube ; but the phosphorus and the wire were abundantly 

 covered. These were lowered into a tube containing spirits of 

 wine, and after some minutes taken out and rinsed with clean 

 water and again lowered into the soda-water ; but they were still 

 active, nearly as much so as before. The wire and the phosphorus 

 were then placed in washed ether, and on being returned to the 

 soda-water the wire was perfectly inactive, but the phosphorus 

 was as briskly active as before, — the fact being that chemically 

 clean platinum wire is not nuclear, but chemically clean phos- 

 phorus is. 



As every thing exposed to the air of a room or to the touch 

 takes more or less a deposit or film of foreign matter, substances 

 may be conveniently classed as catharized or uncatharized accord- 

 ing as they have been or not so freed from foreign matter. 



And it is perhaps not taking too much license with language 

 to extend the term catharized (denoting, as it does, the condition 

 of pure surface) to those substances whose surface has not re- 

 quired the process. Thus a flint stone in the rough has an 

 uncatharized surface, and when immersed in soda-water becomes 

 instantly covered with bubbles ; but split it, and the inner sur- 

 face of the pieces will for a time be clean, and if put into soda- 

 water will not have a single bubble of gas upon it. 



On the other hand, some forms of matter, although perfectly 

 clean, become covered with bubbles the moment they are im- 

 mersed in a supersaturated gaseous solution. Thus, newly formed 

 fragments of a lump of resin, or of a roll of sulphur, or of a block 



* The soda-water used in these experiments was obtained from a conve- 

 nient portable apparatus known as a " Seltzogene." 



