[alt-photo] Re: Math mystery

[Alberto Novo]

Jacques, 

> I think that the explanation of Kees answers this mystery: if the "37%
> formaldehyde" is in fact considered as full strength/100%, then of course
> the 25ml are very near to a 3% solution in a total volume of 1000ml. The
> "mystery" came from my ignorance of this equivalence.

You have already got the solution, but I don't think you have to blame 
yourself for your "ignorance". Sometimes formulae are written wrong or, say, 
in a too simple way. They work, though.
A couple of examples:
 - gum arabic solution 30%, add 30 g of gum to 100 cc of water.
 - classic VDB formulation: 10 g FAC in 33 cc of water, 1.5 g tartaric acid 
in 33 cc H2O, 3.8 g silver nitrate in 33 cc H2O. If one mixes parts of these 
solutions, say 2+2+2 cc, ends with a ratio among the three chemicals which 
is slightly different from that of the whole A+B+C solutions. 

Alberto
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