From: joerdens.jan@googlemail.com   
      
   Eric Lucas schrieb am Mittwoch, 9. Oktober 1996 um 09:00:00 UTC+2:   
   > Gabriel Tojo wrote:   
   > >    
   > > For those new to this thread, this was the first posting:   
   > >    
   > > >You approach a lighter flame to a sugar cube and it does not burn. But   
   > > >if you apply previously some cigarette ash to the cube, it burns.   
   > > >There must be some catalyst in the cigarette ash to sustain the   
   > > >combustion of the sugar cube. Any idea?   
   > >    
   > > It seems that there was a solid consensus within this group supporting   
   > > the wick theory, but Ralph Puchta from Bavaria passed me the following   
   > > information:   
   > >    
   > > łI never tried this experiment, but I'll report an explanation I found   
   > > in:   
   > > Hermann Römpp, Herrmann Raaf, Organische Chemie im Probierglas,   
   > > Franckh'sche Verlagsbuchhandlung Stuttgart, 1982, 15. Auflage. Page   
   > > 108.   
   > > (A nice little book for interested persons.)   
   > >    
   > > The author explanes, that he tested the problem himself and found that   
   > > a   
   > > few drops of FeCl3-solution will do the same job. So his idee was,   
   > > that iron   
   > > salts, you can find in cigarette ash, will behave as a sort of   
   > > catalyst. He   
   > > found that ZnO, K2CO3, Na2CO3, SiO2, and Pb(CH3COO)2 will work, too.   
   > >    
   > > The author denies, that the ash will work as a wick. He thinks, that   
   > > if it would work like a wick, every similiar stuff like whitening   
   > > should allow to burnsugar cubes in   
   > > this easy way˛.   
   > >    
   > > I will get hold of the article in the little book and tell the group   
   > > about it.   
   > >    
   > > Gabriel Tojo   
   > If you recall, I suggested the catalyst explanation very early in the   
   > thread. My suggestion was alkaline oxides and carbonates deprotonating   
   > the sugar alcohols, rendering them more susceptible to electron-transfer   
   > oxidation. Apparently from what you say, acids work as well (e.g.   
   > FeCl3). In this case, I would guess that acids catalyze the dehydration   
   > of the sugar to an olefin or ketone, which can then undergo oxidation   
   > more readily than an alcohol.   
   > However, I thought the data in this case supported the fact that any   
   > sufficiently high surface area solid that is wetted by sugar would   
   > work. For example, I thought that someone said that talc worked.   
   > Just because things that can act as catalysts will work doesn't mean   
   > that is isn't still at keast partly a wicking phenomenon. The   
   > definitive experiment is to try it with something that has little or no   
   > chance of catalyzing the oxidation reaction--for example, very fine   
   > fumed silica would be a good place to start (silated to rid the surface   
   > of acidic--ie catalytic--functionality). Then if it burns under those   
   > conditions, you have proven that the wicking phenomenon is at least part   
   > of the explanation under some conditions.   
   > Eric Lucas   
      
   Hey guys, any new ideas regarding the problem?   
   I am very interested as I am unsure about showing students the combustion of   
   sucrose with ash as an example of a catalysed reaction.   
      
   Jan Jördens   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)