[alt-photo] Re: Math mystery
jacqueskv at gmail.com
Fri Mar 1 10:18:07 GMT 2013
Thanks, Alberto -- I got it.
..and I won't beat myself for my ignorance :-)
2013/3/1 Alberto Novo <alt.list at albertonovo.it>
>> 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.
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