Dorymae
Well-Known Member
I may be wrong here but from the way I read your post I believe you are under the false assumption that the white residue we call soda ash is in fact lye. It is not.
Ash or Mold, Quick Responce Apprecated.
- Thread starter Shalisk
- Start date
Help Support Soapmaking Forum:
I may be wrong here but from the way I read your post I believe you are under the false assumption that the white residue we call soda ash is in fact lye. It is not.
ngian
Well-Known Member
Well I thought that when lye meets the air it turns to soda ash... is that not correct? I have the assumption that soda ash is the lye's reaction with air, instead of reacting with an oil.
I can also see soda ash on the screw lid of my 50% lye solution bottle.
Last edited:
Dorymae
Well-Known Member
I really don't know - I just know that soda ash is not lye - whether it is formed by lye I'm not sure. This would definitely be a question for DeeAnna.
Perhaps some types of soda ash are formed by using up lye (in lye heavy soap) and perhaps there are other ways for it to form. ( thinking out loud here) Honestly I never gave it much thought.
For some reason, I don't think it will affect superfat or lye discounting.
Again, I'm not a scientist, and I have been wrong before, I would wait for DeeAnna to answer.
Perhaps some types of soda ash are formed by using up lye (in lye heavy soap) and perhaps there are other ways for it to form. ( thinking out loud here) Honestly I never gave it much thought.
For some reason, I don't think it will affect superfat or lye discounting.
Again, I'm not a scientist, and I have been wrong before, I would wait for DeeAnna to answer.
Yes, lye will react with carbon dioxide (CO2) in the air to form soda ash (Na2CO3). See Post 17 above. For a brief time, there will be a bit of free NaOH on the surface of the soap, but the NaOH doesn't stay intact for long, because NaOH wants to react badly with something else, and the carbon dioxide in the air volunteers for that duty.
The reaction of NaOH with fats to make soap is a "non-linear decay" reaction, meaning the saponification reaction doesn't happen at a constant rate. The reaction starts fast and furious and then slowly dies down over time, similar to the curve shown below.
This "start fast and stop slow" pattern means MOST of the NaOH will be consumed in the first few hours, but a small amount of the lye can remain unreacted for some hours or days afterwards. How much and how long will depend on the recipe and the way the soap is made. That lingering small amount of NaOH is what can react with CO2 to form soda ash. The amount of lye lost to ash appears to be fairly small in most cases. If the loss was large, I would expect to see soap bars entirely covered with a thick layer of furry crystals, rather than the usual speckling of spots here and there.
Yes, the loss of NaOH to ash will increase the "hidden superfat" in a soap, but I personally think this is a small loss. Even if I did want to worry about it, I don't think it would be easy to calculate -- ash formation varies so much from batch to batch, so how can we accurately predict this?
I am much more concerned about the "hidden superfat" built into most soap recipes because most soap calcs assume NaOH is 100% pure. We all know it's not, even right from the supplier. And as we open and close the lye container, the NaOH purity rapidly drops just because we're allowing CO2 and water from the air into the container. Every soap recipe made with an online soap calc automatically has at least 5% of "hidden superfat" built in. That, to me, is a much larger concern than the loss of NaOH to ash.
"...the density of soap molecules that helps or not the soda-ash formation. It states that if we pour our soap in the mold in light trace the density of the soap molecules is low so the water can walk through more easily to reach soap's surface than in soap that are poured while thick trace in the mold where soap's molecules density is high. The video also states that it is also for the % of humidity in the environment where the soap cures that helps or not soda-ash...."
There are bits of truth in these statements, but I'd say the level of trace when the soap is poured is honestly not an issue. Every soap goes through "thin trace", so whether that happens in the soap pot or in the mold is a moot point. Quite frankly, any time NaOH is exposed to air (really, exposed to CO2), it is forming soda ash. This happens in the NaOH storage container, in the lye pitcher, in the soap pot, in the mold, and on the bars after they are cut. The more concentrated the NaOH is, the more soda ash is made in a given amount of time. You might not see the ash formed when NaOH reacts in the lye pitcher or soap pot, but it's still there -- it's just mixed into the soap rather than visible on the surface.
What I'd say is more of an issue about ash formation on the soap's surface is the total amount of water in the soap after it is poured into the mold. More water can transport more NaOH to the soap's surface. More NaOH on the surface of the soap means more ash can form.
The humidity while the soap cures might be an issue for the first few days of cure, but doesn't seem to be a big issue after that time, in my experience. If ash is going to form after the bars are cut, it usually happens within the first few days of cure.
The reaction of NaOH with fats to make soap is a "non-linear decay" reaction, meaning the saponification reaction doesn't happen at a constant rate. The reaction starts fast and furious and then slowly dies down over time, similar to the curve shown below.
This "start fast and stop slow" pattern means MOST of the NaOH will be consumed in the first few hours, but a small amount of the lye can remain unreacted for some hours or days afterwards. How much and how long will depend on the recipe and the way the soap is made. That lingering small amount of NaOH is what can react with CO2 to form soda ash. The amount of lye lost to ash appears to be fairly small in most cases. If the loss was large, I would expect to see soap bars entirely covered with a thick layer of furry crystals, rather than the usual speckling of spots here and there.
Yes, the loss of NaOH to ash will increase the "hidden superfat" in a soap, but I personally think this is a small loss. Even if I did want to worry about it, I don't think it would be easy to calculate -- ash formation varies so much from batch to batch, so how can we accurately predict this?
I am much more concerned about the "hidden superfat" built into most soap recipes because most soap calcs assume NaOH is 100% pure. We all know it's not, even right from the supplier. And as we open and close the lye container, the NaOH purity rapidly drops just because we're allowing CO2 and water from the air into the container. Every soap recipe made with an online soap calc automatically has at least 5% of "hidden superfat" built in. That, to me, is a much larger concern than the loss of NaOH to ash.
"...the density of soap molecules that helps or not the soda-ash formation. It states that if we pour our soap in the mold in light trace the density of the soap molecules is low so the water can walk through more easily to reach soap's surface than in soap that are poured while thick trace in the mold where soap's molecules density is high. The video also states that it is also for the % of humidity in the environment where the soap cures that helps or not soda-ash...."
There are bits of truth in these statements, but I'd say the level of trace when the soap is poured is honestly not an issue. Every soap goes through "thin trace", so whether that happens in the soap pot or in the mold is a moot point. Quite frankly, any time NaOH is exposed to air (really, exposed to CO2), it is forming soda ash. This happens in the NaOH storage container, in the lye pitcher, in the soap pot, in the mold, and on the bars after they are cut. The more concentrated the NaOH is, the more soda ash is made in a given amount of time. You might not see the ash formed when NaOH reacts in the lye pitcher or soap pot, but it's still there -- it's just mixed into the soap rather than visible on the surface.
What I'd say is more of an issue about ash formation on the soap's surface is the total amount of water in the soap after it is poured into the mold. More water can transport more NaOH to the soap's surface. More NaOH on the surface of the soap means more ash can form.
The humidity while the soap cures might be an issue for the first few days of cure, but doesn't seem to be a big issue after that time, in my experience. If ash is going to form after the bars are cut, it usually happens within the first few days of cure.
Last edited:
Dorymae
Well-Known Member
I knew you would be able to explain! One quick question, if it does increase superfat would it be enough to raise it by a percentage point or is it insignificant? Or am I just splitting hairs to think we should use a lower superfat to compensate?
"... if it does increase superfat would it be enough to raise it by a percentage point or is it insignificant? Or am I just splitting hairs to think we should use a lower superfat to compensate? ..."
Hey, Dorymae -- my honest answer is I don't know. Even if ash does increase the superfat significantly, the amount is going to vary with the recipe and the method used to make the soap, so it's going to be tough to predict accurately.
Like I said earlier -- I personally am not overly concerned about increased superfat due to ash formation. I am much more concerned about the "hidden superfat" built into most soap recipes because most soap calcs assume NaOH is 100% pure.... Every soap recipe made with an online soap calc automatically has at least 5% of "hidden superfat" built in. That, to me, is a much larger concern than the loss of NaOH to ash.
I don't do any adjustment of my lye to compensate for ash, since I don't know how I can realistically account for that error. I do have a correction built into my personal soap recipe calc for lye purity. I also use a relatively low superfat nowadays -- usually around 2-3%.
If you use an online calc, you can correct for lye purity as a separate calculation:
1. Use your favorite online calc to finalize your ingredients using the superfat % you want to use. Every calc I've checked is set at 100% purity for NaOH. The 100 in the formula below is this 100% "ideal NaOH purity" built into the calcs.
2. Decide what your actual lye purity is. As delivered, Essential Depot NaOH and Lye Guy NaOH are roughly 95% purity. NaOH from other suppliers may be different than ED and the Lye Guy's stuff. As time goes on, this purity will drop (see Post 24 above), so you might want to reduce this purity by a percent or so every time you use NaOH from an existing opened container. (Yes, this is a guess, but it's a better guess than assuming the NaOH stays at 95% or whatever.)
3. Calculate the actual lye weight you should measure out based on the purity:
Actual NaOH weight = Ideal NaOH weight * 100 / Actual NaOH % purity
Example: I need 137 grams of NaOH at Soapcalc's purity of 100%. What is the actual amount of NaOH I should weigh out if my actual NaOH is only 94% pure?
Actual NaOH weight = 137 g * 100 / 94 = 145.7 g
See how the actual weight of NaOH goes UP compared with the ideal weight? That's what you want to see -- more weight, not less. The extra weight is the weight of extra the impurities in your actual NaOH. You can't get rid of the impurities, but you can measure out a little more lye to compensate.
Hey, Dorymae -- my honest answer is I don't know. Even if ash does increase the superfat significantly, the amount is going to vary with the recipe and the method used to make the soap, so it's going to be tough to predict accurately.
Like I said earlier -- I personally am not overly concerned about increased superfat due to ash formation. I am much more concerned about the "hidden superfat" built into most soap recipes because most soap calcs assume NaOH is 100% pure.... Every soap recipe made with an online soap calc automatically has at least 5% of "hidden superfat" built in. That, to me, is a much larger concern than the loss of NaOH to ash.
I don't do any adjustment of my lye to compensate for ash, since I don't know how I can realistically account for that error. I do have a correction built into my personal soap recipe calc for lye purity. I also use a relatively low superfat nowadays -- usually around 2-3%.
If you use an online calc, you can correct for lye purity as a separate calculation:
1. Use your favorite online calc to finalize your ingredients using the superfat % you want to use. Every calc I've checked is set at 100% purity for NaOH. The 100 in the formula below is this 100% "ideal NaOH purity" built into the calcs.
2. Decide what your actual lye purity is. As delivered, Essential Depot NaOH and Lye Guy NaOH are roughly 95% purity. NaOH from other suppliers may be different than ED and the Lye Guy's stuff. As time goes on, this purity will drop (see Post 24 above), so you might want to reduce this purity by a percent or so every time you use NaOH from an existing opened container. (Yes, this is a guess, but it's a better guess than assuming the NaOH stays at 95% or whatever.)
3. Calculate the actual lye weight you should measure out based on the purity:
Actual NaOH weight = Ideal NaOH weight * 100 / Actual NaOH % purity
Example: I need 137 grams of NaOH at Soapcalc's purity of 100%. What is the actual amount of NaOH I should weigh out if my actual NaOH is only 94% pure?
Actual NaOH weight = 137 g * 100 / 94 = 145.7 g
See how the actual weight of NaOH goes UP compared with the ideal weight? That's what you want to see -- more weight, not less. The extra weight is the weight of extra the impurities in your actual NaOH. You can't get rid of the impurities, but you can measure out a little more lye to compensate.
Last edited:
Dorymae
Well-Known Member
Thank you so much! Once again I have learned some valuable information from you! I never thought about the purity or how much the calculators could be off in regards to lye discount.
Thank you for sharing your knowledge with everyone here!
Thank you for sharing your knowledge with everyone here!
DeeAnna, this is off the top of my head, but I SF pretty high, usually, at b/w 7-8% - all things being equal, ie; not considering, eg., the occasional reduction for a heavy whipping cream soap or the like - and I rarely, if ever, get soda ash. Do you think that could be one of the reasons, ie; the lye is busy linking up with all of the fat molecules? I don't really know if that makes sense, ie; if you superfat at all, even at low amounts, it seems as if it would get used up and that any remainder is just kind of randomly free-floating for its own insidious reasons.
I'm not convinced that a soap with a modestly high superfat would necessarily make any less ash than soap with a lower superfat, all other things being equal. A soap made with a superfat probably does make less ash compared with a soap made with excess lye, again all other things being equal. On the other hand, once you have an excess of a reactant (fat), then adding more of that reactant doesn't necessarily improve matters as much as you might want.
It's like a high school dance. If there are a few more girls (fats) than guys (lye), it's statistically more likely that a given guy will be able to find a girl to dance with. But if there are, say, twice as many girls than guys, his chances will improve somewhat, but I don't think he will be twice as likely to find a girl to dance with.
Once the lye makes it to the surface of the bar, the game changes significantly. There's not only fat to react with, there is now CO2 to react with. Lye will STRONGLY want to react with CO2 rather than the fat, because it's so much easier. Reacting with a fat molecule means the lye has to do a lot of work -- first strip off a fatty acid from the fat, and then react with the fatty acid to make a soap molecule. This requires more energy and time than reacting with cute little CO2 molecules to make soda ash.
Getting back to the high school dance: The guys (lye) are circulating at the school dance scoping out the girls (fats). The guys in the middle of the dance floor are surrounded by lots of girls, but the problem is the guys have to make small talk and actually have to dance with the girls to have any hope of getting to "first base" with a girl (fatty acid). What the guys in the middle of the dance floor don't know, however, is right outside the dance hall doors are a few cute, but naughty girls (CO2). The guys who are at the edge of the dance hall see these girls hanging around outside, and sure nuff they sneak out to be with them instead. Why should they do all the work of meeting a girl at the dance, when there is a fun party to enjoy outside?
(I want to point out my father was a high school teacher and a strict father. I was most emphatically not one of those cute girls outside -- if I was, I doubt I would be here to tell you these silly little stories!)
There are a lot of variables that go into whether a soap makes ash or not, so it's hard to point at any one variable (such as superfat) and say it and only it determines whether there is ash on a soap or not. It might be ... but it might not.
It's like a high school dance. If there are a few more girls (fats) than guys (lye), it's statistically more likely that a given guy will be able to find a girl to dance with. But if there are, say, twice as many girls than guys, his chances will improve somewhat, but I don't think he will be twice as likely to find a girl to dance with.
Once the lye makes it to the surface of the bar, the game changes significantly. There's not only fat to react with, there is now CO2 to react with. Lye will STRONGLY want to react with CO2 rather than the fat, because it's so much easier. Reacting with a fat molecule means the lye has to do a lot of work -- first strip off a fatty acid from the fat, and then react with the fatty acid to make a soap molecule. This requires more energy and time than reacting with cute little CO2 molecules to make soda ash.
Getting back to the high school dance: The guys (lye) are circulating at the school dance scoping out the girls (fats). The guys in the middle of the dance floor are surrounded by lots of girls, but the problem is the guys have to make small talk and actually have to dance with the girls to have any hope of getting to "first base" with a girl (fatty acid). What the guys in the middle of the dance floor don't know, however, is right outside the dance hall doors are a few cute, but naughty girls (CO2). The guys who are at the edge of the dance hall see these girls hanging around outside, and sure nuff they sneak out to be with them instead. Why should they do all the work of meeting a girl at the dance, when there is a fun party to enjoy outside?
(I want to point out my father was a high school teacher and a strict father. I was most emphatically not one of those cute girls outside -- if I was, I doubt I would be here to tell you these silly little stories!)
There are a lot of variables that go into whether a soap makes ash or not, so it's hard to point at any one variable (such as superfat) and say it and only it determines whether there is ash on a soap or not. It might be ... but it might not.
Last edited:
ngian
Well-Known Member
Thank you DeeAnna for your valuable response.
I guess the next paragraph sums up the answer to my general question around soda ash:
but arises another question:
I have been told by another soaper that when NaOH is in a from of 50% lye solution, it will not attract moisture from the air as it has more water than the air. So the whatever purity it has, stays intact. I guess that humidity(water) from the air is the carrier for the CO2 to react with NaOH. I also guess that water will evaporate instead from the 50% lye solution and I don't know if this affects in a large scale the purity or mainly the amount. Which of the above are true?
I have also seen that soapcalc that I always use, computes the amount of NaOH that a recipe needs a bit different maybe to compete the not always clear NaOH that we have. I have calculated a recipe by hand using SAP values of a Castile recipe having 5% lye discount, and when I put that in soapcalc it gave me a real lye discount of around 4,7%.
I have seen that every 1% in lye discount in Olive's oil SAP(0,135) is 1,35gr of NaOH difference when doing it by hand:
0% = 135gr
1% = 135gr-(1,35x1) = 133,65gr
2% = 135gr-(1,35x2) = 132,3gr and so on...
But soapcalc arises the amount of NaOH by 0.47gr
0% = 135,47gr
1% = 134,12gr
2% = 132,76gr
I know this second matter is not straightly associated with soda-ash though but just found the space to mention it
Nikoshttp://www.soapmakingforum.com//www.pinterest.com/pin/create/extension/
I guess the next paragraph sums up the answer to my general question around soda ash:
but arises another question:
I have been told by another soaper that when NaOH is in a from of 50% lye solution, it will not attract moisture from the air as it has more water than the air. So the whatever purity it has, stays intact. I guess that humidity(water) from the air is the carrier for the CO2 to react with NaOH. I also guess that water will evaporate instead from the 50% lye solution and I don't know if this affects in a large scale the purity or mainly the amount. Which of the above are true?
I have also seen that soapcalc that I always use, computes the amount of NaOH that a recipe needs a bit different maybe to compete the not always clear NaOH that we have. I have calculated a recipe by hand using SAP values of a Castile recipe having 5% lye discount, and when I put that in soapcalc it gave me a real lye discount of around 4,7%.
I have seen that every 1% in lye discount in Olive's oil SAP(0,135) is 1,35gr of NaOH difference when doing it by hand:
0% = 135gr
1% = 135gr-(1,35x1) = 133,65gr
2% = 135gr-(1,35x2) = 132,3gr and so on...
But soapcalc arises the amount of NaOH by 0.47gr
0% = 135,47gr
1% = 134,12gr
2% = 132,76gr
I know this second matter is not straightly associated with soda-ash though but just found the space to mention it
Nikoshttp://www.soapmakingforum.com//www.pinterest.com/pin/create/extension/
Many people notice flakes on top of their solution which is the lye IN the solution reacting with the CO2 to make what is essentially soda ash but floating on top of the lye solution. This in itself would reduce the amount of lye in your solution and mean that, per 100g solution, you would have less than 50g lye
"...when NaOH is in a from of 50% lye solution, it will not attract moisture from the air as it has more water than the air..."
Not true. As Effy says, you can verify that for yourself.
"...I also guess that water will evaporate instead from the 50% lye solution..."
Yes, it can if you don't keep it in a tightly closed container. If a person wants to masterbatch a 50% lye solution, they need to keep it in a tightly closed container with as little headspace (air) in the container as possible. This is the only way to ensure the solution remains as stable as possible.
"...I have seen that every 1% in lye discount in Olive's oil SAP(0,135) is 1,35gr of NaOH difference when doing it by hand... But soapcalc arises the amount of NaOH by 0.47gr ..."
That's because the sap value for olive oil in Soapcalc is 0.1355, not 0.1350. The extra 0.005 is not shown in the display in the first screen of Soapcalc, but the number used in the calculations does include it. That's why you're seeing a discrepancy in your math vs. Soapcalc math.
Not true. As Effy says, you can verify that for yourself.
"...I also guess that water will evaporate instead from the 50% lye solution..."
Yes, it can if you don't keep it in a tightly closed container. If a person wants to masterbatch a 50% lye solution, they need to keep it in a tightly closed container with as little headspace (air) in the container as possible. This is the only way to ensure the solution remains as stable as possible.
"...I have seen that every 1% in lye discount in Olive's oil SAP(0,135) is 1,35gr of NaOH difference when doing it by hand... But soapcalc arises the amount of NaOH by 0.47gr ..."
That's because the sap value for olive oil in Soapcalc is 0.1355, not 0.1350. The extra 0.005 is not shown in the display in the first screen of Soapcalc, but the number used in the calculations does include it. That's why you're seeing a discrepancy in your math vs. Soapcalc math.
Last edited:
I wrote earlier:
' "...I also guess that water will evaporate instead from the 50% lye solution..." '
'...Yes, it can if you don't keep it in a tightly closed container. ...'
And I should explain more, since I bet that sounds confusing.
Sodium hydroxide is "deliquescent" meaning it is a chemical that quickly absorbs water from the air to form a solution of sodium hydroxide and water. The concentration of this lye solution, assuming you could measure it, will vary depending on the time, humidity, temperature, and amount of lye present. The concentration can be saturated (up to about 52% NaOH), but it is quite likely to be lower. The concentration will be difficult to measure, however, because there is another process rapidly happening at the same time --
While the lye is madly soaking up water from the air, it is also quickly reacting with any CO2 to form soda ash. The rate of conversion will depend on the surface area of the solution that is exposed to the air, the concentration of CO2 in the nearby air, the concentration of the lye solution, and the temperature.
After enough time, the lye solution will decompose into a solution of soda ash and water. Soda ash is not deliquescent, so water CAN and does evaporate out of solution. Given enough time and moderate to low humidity, the water in this solution can evaporate completely, leaving behind a white crust of soda ash and the minerals from the water.
That is why a bead of lye spilled onto your counter or floor will first turn into a droplet of liquid (lye-water solution) that can burn your skin and then after a few hours the liquid will no longer burn the skin and will eventually dry into a small crusty white spot.
' "...I also guess that water will evaporate instead from the 50% lye solution..." '
'...Yes, it can if you don't keep it in a tightly closed container. ...'
And I should explain more, since I bet that sounds confusing.
Sodium hydroxide is "deliquescent" meaning it is a chemical that quickly absorbs water from the air to form a solution of sodium hydroxide and water. The concentration of this lye solution, assuming you could measure it, will vary depending on the time, humidity, temperature, and amount of lye present. The concentration can be saturated (up to about 52% NaOH), but it is quite likely to be lower. The concentration will be difficult to measure, however, because there is another process rapidly happening at the same time --
While the lye is madly soaking up water from the air, it is also quickly reacting with any CO2 to form soda ash. The rate of conversion will depend on the surface area of the solution that is exposed to the air, the concentration of CO2 in the nearby air, the concentration of the lye solution, and the temperature.
After enough time, the lye solution will decompose into a solution of soda ash and water. Soda ash is not deliquescent, so water CAN and does evaporate out of solution. Given enough time and moderate to low humidity, the water in this solution can evaporate completely, leaving behind a white crust of soda ash and the minerals from the water.
That is why a bead of lye spilled onto your counter or floor will first turn into a droplet of liquid (lye-water solution) that can burn your skin and then after a few hours the liquid will no longer burn the skin and will eventually dry into a small crusty white spot.
Last edited:
In Post #26, I said: "...As time goes on, this purity will drop (see Post 24 above), so you might want to reduce this purity by a percent or so every time you use NaOH from an existing opened container. (Yes, this is a guess, but it's a better guess than assuming the NaOH stays at 95% or whatever.)..."
I had a vague memory at the time that Susie had shared a sensible, easy method to compensate for the drop in NaOH purity with time. I couldn't remember what it was at that moment, but I just now found the info!!! Susie said:
"...I [know] about the purity of NaOH. I also know about the humidity where I live. The difference between soap made with a new bottle of lye and an old bottle is quite large. I have been compensating by using [a superfat of] 5% when [the NaOH] is new, then dropping the superfat by 1% per quarter bottle...."
Source: http://www.soapmakingforum.com/showthread.php?p=446524
I had a vague memory at the time that Susie had shared a sensible, easy method to compensate for the drop in NaOH purity with time. I couldn't remember what it was at that moment, but I just now found the info!!! Susie said:
"...I [know] about the purity of NaOH. I also know about the humidity where I live. The difference between soap made with a new bottle of lye and an old bottle is quite large. I have been compensating by using [a superfat of] 5% when [the NaOH] is new, then dropping the superfat by 1% per quarter bottle...."
Source: http://www.soapmakingforum.com/showthread.php?p=446524
ngian
Well-Known Member
Well does 50% lye solution (50% water & 50% NaOH) is madly soaking water from air although it has so much already? And if it does so much, is its rate of water absorption from the air smaller than when the NaOH is in solid form (flakes) as there is already water in lye?
From all the above I am wondering if it's better to have solid NaOH flakes or 50% lye solution, to avoid the quick loss of purity when someone doesn't care about recipe's affection as it concerns the liquids while it will be used alike (open the jar / bottle the same number of times and for the same time).
The other soaper also told me that someone can measure the purity of NaOH with sulfuric acid... but I don't know if it easy and if someone needs to use other lab instruments too...
Last edited:
"...Well does 50% lye solution (50% water & 50% NaOH) is madly soaking water from air although it has so much already?..."
I really don't know how to answer this in simple terms. You're using "common sense" to answer a chemistry question that doesn't have a "common sense" answer.
NaOH is a deliquescent material, meaning it will continue to "madly" soak up water until there is no more water to soak up. It is so very good at absorbing water from the air that it can be used in the laboratory as a desiccant to dry things to "mummy dryness".
"...And if it does so much, is its rate of water absorption from the air smaller than when the NaOH is in solid form (flakes) as there is already water in lye?..."
Not necessarily. See answer above.
"...From all the above I am wondering if it's better to have solid NaOH flakes or 50% lye solution, to avoid the quick loss of purity..."
Either one has the same issues. Pick your poison, as the saying goes. Keep either in a container with as little headspace (free air) as possible. Don't leave the container open for any longer than necessary and keep the container tightly closed at all other times. Use the material in a reasonable amount of time.
"...The other soaper also told me that someone can measure the purity of NaOH with sulfuric acid..."
Yes that's correct. It's a titration to a pH endpoint. You need to be able to make (or purchase) a standardized acid solution and either a pH indicator or a pH meter.
I really don't know how to answer this in simple terms. You're using "common sense" to answer a chemistry question that doesn't have a "common sense" answer.
NaOH is a deliquescent material, meaning it will continue to "madly" soak up water until there is no more water to soak up. It is so very good at absorbing water from the air that it can be used in the laboratory as a desiccant to dry things to "mummy dryness".
"...And if it does so much, is its rate of water absorption from the air smaller than when the NaOH is in solid form (flakes) as there is already water in lye?..."
Not necessarily. See answer above.
"...From all the above I am wondering if it's better to have solid NaOH flakes or 50% lye solution, to avoid the quick loss of purity..."
Either one has the same issues. Pick your poison, as the saying goes. Keep either in a container with as little headspace (free air) as possible. Don't leave the container open for any longer than necessary and keep the container tightly closed at all other times. Use the material in a reasonable amount of time.
"...The other soaper also told me that someone can measure the purity of NaOH with sulfuric acid..."
Yes that's correct. It's a titration to a pH endpoint. You need to be able to make (or purchase) a standardized acid solution and either a pH indicator or a pH meter.
