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Useful 10% solutions



 
 
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  #12  
Old March 30th 06, 09:53 PM posted to rec.photo.darkroom
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Default Useful 10% solutions

Dana:
Try this 'mind' experiment. Into a beaker, place 10gms of salt. Now add
enough water to dissolve the salt and bring the final volume up to 100ml.
This is a 10% solution. The total weight of the salt in the 100ml of
solution is still 10gms. Now pour off 10ml of the solution. How much salt
will be in the 10ml? Well, since 10ml is 1/10th of the original solution,
it'll contain 1/10th of the total amount that was added originally. 1/10th
of the original 10gms is 1gm. We never need to know the volume of the salt.
THT
-LS
"Dana H. Myers" wrote in message
...
wrote:
REana H. Myers wrote:
I know what the volume of 10 grams of water is.
What's the volume of 10g of NaOH?

I think you're mixing up two different conventions.
Dana


A 10ml solution of 10% NaOH will have 1 gram
of the solute; 10% of the solutions volume. As I said
the solute's amount is usually in grams. Dan


What's the volume of 1 gram of NaOH? Do you think
it is 1 ml? I don't think it is. You're mixing weight
and volume interchangeably here, which you can do with
water but not the solute.

Dana



  #14  
Old March 31st 06, 01:49 AM posted to rec.photo.darkroom
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Default Useful 10% solutions

wrote

My chemists' book speaks of molal, molar, normal,
and some amount of solute in specific amouts of solvent.


All the methods but the useful and easy one: grams/litre


  #15  
Old March 31st 06, 04:14 AM posted to rec.photo.darkroom
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Default Useful 10% solutions

Lew wrote:
Dana:
Try this 'mind' experiment.


I *get* it.

Dana
  #17  
Old March 31st 06, 03:20 PM posted to rec.photo.darkroom
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Default Useful 10% solutions

"Dana H. Myers" wrote

But it isn't 10% of the solution's *volume* unless the solute
has the same density as water. Do the math.


It isn't 10% of the solution's volume unless the solute is water.

Solids dissolved in liquids don't take up the same space - the
dissolved solid occupies the 'voids' [there must be a better word]
between the water molecules.

.... anybody up for discussing Angels dancing on pinheads?


  #18  
Old March 31st 06, 07:35 PM posted to rec.photo.darkroom
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Default Useful 10% solutions

Nicholas O. Lindan wrote:
"Dana H. Myers" wrote

But it isn't 10% of the solution's *volume* unless the solute
has the same density as water. Do the math.


It isn't 10% of the solution's volume unless the solute is water.

Solids dissolved in liquids don't take up the same space - the
dissolved solid occupies the 'voids' [there must be a better word]
between the water molecules.

... anybody up for discussing Angels dancing on pinheads?


Somehow I want to spread my hands in a broad sweeping motion
and declare "billions and billions of starstuff".

;-)
  #19  
Old March 31st 06, 11:09 PM posted to rec.photo.darkroom
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Default Useful 10% solutions

Wayne wrote:

Wayne wrote:


wrote:


"Hydroquinone: To increase the print contrast add 100ml per liter of
working developer."

How does one make a 10% solution of this photo chemical?

the quote comes from,

http://www.jackspcs.com/pitone.htm


Unless you are going to use it immediately you will probably want some
sodium sulfite in this 10% solution too. Its best to start with less
than 1000 ml water and add water to make 1000 after dissolving both the
sulfite and HQ. Otherwise you may end up with slightly more than 1000
ml, and hence a slightly weaker solution. It probably wont make much of
a practical difference in this case but its a good practice to get
into. I'll let someone else suggest how much sulfite you will need.




Since the others seem to be occupied, I will recommend adding roughly
30 grams of sodium sulfite to preserve your 10% solution. Jackspsc
recommends adding some sodium bisulfite too, which may be helpful but
it is probably optional if you dont happen to have any laying around.

HYDROQUINONE SOLUTION
Chemical Amount Units
Water (125°F/52°C) 750 ml
Sodium sulfite 25 g
Sodium bisulfite* 5 g
Hydroquinone 10 g
Water to make 1000 ml

* The sodium bisulfite is not in the original formula. Maxim Muir
recommends it to buffer the hydroquinone solution.
http://www.jackspcs.com/pd130a.htm



That is only 1/10 %.
If you want a long lived solution of hydroquinone without preservative,
use Propylene glycol instead of water as the solvent. Hydroquinone,
pyrogallol, paraminophenol base (not the hydrochloride), and
pyrocatechol are all soluble enough in glycol to make a 10% solution
which will then dissolve in water. By 10% I mean 100 grams dissolved in
enough glycol to make 1 liter.


  #20  
Old March 31st 06, 11:48 PM posted to rec.photo.darkroom
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Default Useful 10% solutions

1%?
"PATRICK GAINER" wrote in message
...
HYDROQUINONE SOLUTION
Chemical Amount Units
Water (125°F/52°C) 750 ml
Sodium sulfite 25 g
Sodium bisulfite* 5 g
Hydroquinone 10 g
Water to make 1000 ml



That is only 1/10 %.



 




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