[Alt-photo] mixing solution

`Richard Knoppow dickburk at ix.netcom.com
Wed May 10 18:59:49 UTC 2017


    Its a good rule to follow to add solid to liquid or a concentrate of 
any sort to the diluent but the rule comes from the exothermic reaction 
of dissolving some chemicals, both acids and bases. For instance sodium 
hydroxide is very exothermic and will cause boiling and splattering of 
the mixture, which is very corrosive. Crystalline thiosulfate, OTOH, is 
endothermic and must be mixed with heated water. In fact, mixing some 
crystalline thiosulfate in a surrounding bath was a method of cooling 
when ice was not available.
    A good rule of thumb is to mix powder or crystalline material slowly 
with just enough stirring to keep it suspended so as not to beat air 
into the mixture.

On 5/10/2017 8:56 AM, Loris Medici via Alt-photo-process-list wrote:
> Never add water into acid!!! That's rule #1 when working with acids.
>
> You may add 600ml water into a 1000-1500ml beaker, then add citric acid
> constantly stirring and then add more water to make 1000ml.
>
> If I remember correctly, mixing citric acid into water is endothermic (the
> solution temperature goes down...), therefore you may opt to warm the water
> beforehand; (to 40-50C in the microwave owen) the acid will go into
> solution faster...
>
>
> On May 10, 2017 6:44 PM, "Bob Cornelis via Alt-photo-process-list" <
> alt-photo-process-list at lists.altphotolist.org> wrote:
>
>> I am using Ware cyanotype and want to try his suggestion of adding some 40%
>> citric acid solution to sensitizer to allow it to work with a wider range
>> of papers. I'm not used to mixing this high a concentration of solid to
>> liquid so am looking for the correct procedure.
>>
>> If I wanted to end up with 1 liter of this solution, would I start with
>> 400gms of citric acid and add water to make 1 liter?
>>
>> Thanks
>> Bob
>>

-- 
Richard Knoppow
dickburk at ix.netcom.com
WB6KBL



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