CS: Target-BP corrosiveness & Remedial Chemistry lesson

[EVANS,CHRIS \(HP-Unitedkingdom,ex1\)]

From:   "EVANS,CHRIS (HP-Unitedkingdom,ex1)", [EMAIL PROTECTED]

Science will beat the anoraks any day.

> Chemically, the empirical formula for combustion of Black
> Powder can be written as follows:
>                                        Heat>
> 4KNO4 + 7C + 2S = K2CO3 + K2S2 + 3CO2 + 2N2
> 

This is plain wrong, the components don't add up.  There are
3 fewer Carbon atoms and 7 fewer Oxygen atoms on the RHS of 
this formula than on the left.  Transmutation?

A better description is:

16KNO3 + 21C + 5S = 5K2CO3 + 2K2S2 + K2SO4 + 13CO2 + 3CO + 8N2
                    (+heat)

however even this is a misleading simplification in any
practical application.

Firstly, not all of the components will react fully - there
will be KNO3, elemental C and S residues.  Even those components that react
will not do so in a uniform manner leading to the formation of other
products.

Secondly, there are other materials present in the reaction, 
such as H2O (oh yes) and air (donating, amongst others, Oxygen,
Hydrogen and Nitrogen to the reaction).  Not to mention the
chemical contributions from the percussion cap in our case.

All of this means that the exact range and quantity of combustion
products is not known with certainty.  Your nose should tell you 
that there is H2S present (bad eggs smell).  This shows that there is
hydrogen available to the reaction (necessary for acid formation).

In real combustions, there are many other products found in varying
(small) quantities - including acids. 

> Try something for yourself, put some BP in a glass of water,
> shake it up and test it with litmus paper (or Methyl Orange
> if you can get it) - you will find no reaction! (try the
> same on some powder fouling if you like - you will get the
> same result)

Bad test.  The overall ph of the solution may be neutral, acid, or
base, it tells you nothing about the individual components of the 
products of combustion before they were dissolved and uniformly 
mixed in water. 

Chris


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