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#11
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Useful 10% solutions
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#12
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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 |
#13
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Useful 10% solutions
REana H. Myers wrote:
wrote: 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. We are not interested in the volume of that 1 gram of NaOH. We are only interested in the NaOH being 10% of the solutions volume expressed in grams. Do the math. If you need 1 liter of solution of 12.5 % concentration dissolve 125 grams of the solute in some of the solvent then bring the solution volume to 1 liter. 12.5 % of 1000 is 125; grams in this case. It could be some volume of gas or weight or volume of fluid for that matter. It's a darkroom way of compounding chemistry. Likely the same method is used more universally. My chemists' book speaks of molal, molar, normal, and some amount of solute in specific amouts of solvent. Dan |
#14
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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
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Useful 10% solutions
Lew wrote:
Dana: Try this 'mind' experiment. I *get* it. Dana |
#17
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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
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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
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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
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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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