[alt-photo] Re: Math mystery

[Johnny Brian]

The 37% is on a weight basis. Although it is a gas, it is also a solute. As pointed out, it is a saturated solution. Concentrations should be expressed in correct terms to avoid confusion. Saying 37% = 100% is confusing. 

I also agree that formaldehyde is toxic, and I wouldn't use it at home. I've used it the lab over the years, but we have fume hoods to deal with it. I also believe formaldehyde can have residual metals in the solution - don't know how this might impact alt chemistry. 

Johnny Brian

On Feb 28, 2013, at 15:38, Kees Brandenburg <workshops at polychrome.nl> wrote:

> 
> 
>> So, when using a 37% solution of formalin, I would think that you have to
>> use around 80ml of the formalin solution...
> 
> Jacques,
> 
> Formalin is a 37% solution of formaldehyde gas in water. This is considered as full strenght (= 100%) formalin. If a recipe asks for 25ml undiluted formalin in 1 liter water this is  a 2,5%  formalin solution. Your correction by adding 80ml instead of 25 ml to compensate for the 37% formaldehyde solution in formalin is wrong. You end up with a too strong mix! 
> 
> Anyway I should try to avoid formalin alltogether.
> 
> Kees
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