How is this calculated?

[sofie]

I am reading an article for my thesis in paintings conservation and I've come across some calculations that I can't seem to figure out. A type of absorbing tissue called Evolon is supposed to be kept overnight in a sealed container "loaded with ethanol". Strips of Evolon measuring 2 x 5 cm2 are placed in two different containers, one with 34% ethanol (87.4 mg Evolon / 102.7 mg ethanol) and one with 51% ethanol (92.3 mg Evolon / 149.1 mg ethanol). The numbers in the parentheses are given by the authors. I don't see how they relate to the percentage values. 

Can anyone explain to me how I can calculate the right amount of ethanol to a given amount of Evolon tissue?

[CharonY]

That looks weird. From what I understand you have a tissue strip of a fixed size (and therefore weight) and load it with ethanol at a given percentage. I do not understand why the Evolon (if that refers to the strip) then changes in weight. Intuitively I would have assumed that you would soak the tissue with 51% and 34%, ethanol, respectively. I can only speculate, but is it possible that the did just that and the weight difference is because the cut strips had the respective weight differences (i.e. 92 vs 87 mg) and they tried to account the total ethanol content for that (the numbers still seem a little bit off, maybe someone else has a better idea)?

[studiot]

40 minutes ago, sofie said:

I am reading an article for my thesis in paintings conservation and I've come across some calculations that I can't seem to figure out. A type of absorbing tissue called Evolon is supposed to be kept overnight in a sealed container "loaded with ethanol". Strips of Evolon measuring 2 x 5 cm2 are placed in two different containers, one with 34% ethanol (87.4 mg Evolon / 102.7 mg ethanol) and one with 51% ethanol (92.3 mg Evolon / 149.1 mg ethanol). The numbers in the parentheses are given by the authors. I don't see how they relate to the percentage values. 

Can anyone explain to me how I can calculate the right amount of ethanol to a given amount of Evolon tissue?

Are you sure you have copied out exactly what the article says and got the milligrams and millilitres (if there were any) right?
Ethanol is not normally specified by weight, though it may be.

Can you not link us to the actual article (+page number preferred)?

University Products says their Evolon is 130 g per square metre, which is different from your figures, though in the same ballpark.

The %s given certainly do not match the ratio of ethanol to the combined weights of ethanol and evolon stated.

 

[Sensei]

1 hour ago, sofie said:

I am reading an article for my thesis in paintings conservation and I've come across some calculations that I can't seem to figure out. A type of absorbing tissue called Evolon is supposed to be kept overnight in a sealed container "loaded with ethanol". Strips of Evolon measuring 2 x 5 cm2 are placed in two different containers, one with 34% ethanol (87.4 mg Evolon / 102.7 mg ethanol) and one with 51% ethanol (92.3 mg Evolon / 149.1 mg ethanol). The numbers in the parentheses are given by the authors. I don't see how they relate to the percentage values. 

Can anyone explain to me how I can calculate the right amount of ethanol to a given amount of Evolon tissue?

I am guessing 34% and 51% means concentration of ethanol mixed with water (or other solvent) by volume..

Density of pure ethanol is ~0.789 g/mL so:

102.7 mg / 0.79 g/mL = 0.1027 g / 0.79 g/mL = ~0.13 mL of ethanol by volume

149.1 mg / 0.79 g/mL = 0.1491 g / 0.79 g/mL = ~0.188 mL of ethanol by volume

34% of ethanol and 66% of water/solvent will have total volume 0.13/0.34 = ~0.37 mL

51% of ethanol and 49% of water/solvent will have total volume 0.188/0.51 = ~0.37 mL. So they matches.

 

 

Edited November 4, 2019 by Sensei

[sofie]

The article can be downloaded from this link: 
https://www.researchgate.net/publication/333190051_Solvent-mediated_extraction_of_fatty_acids_in_bilayer_oil_paint_models_a_comparative_analysis_of_solvent_application_methods
The description is on page 3 under "Simulated cleaning test procedure"

I agree that it looks weird. It could be that they are simply referring to 34% and 51% of ethanol in water and not some weight/weight ratio between Evolon and ethanol. I partly came to that conclusion myself but couldn't seem to get the numbers to match. Could it be that the weights listed for Evolon and ethanol are the weights of the individual Evolon strips and the amount of ethanol absorbed into the tissue? 

So, if I were to try this procedure myself I could soak Evolon tissue in an unspecified amount of ethanol as long as it is 34% or 51%?

Thank you for your replies so far!

[sofie]

On 11/4/2019 at 7:21 PM, studiot said:

Are you sure you have copied out exactly what the article says and got the milligrams and millilitres (if there were any) right?
Ethanol is not normally specified by weight, though it may be.

Can you not link us to the actual article (+page number preferred)?

University Products says their Evolon is 130 g per square metre, which is different from your figures, though in the same ballpark.

The %s given certainly do not match the ratio of ethanol to the combined weights of ethanol and evolon stated.

 

 

On 11/4/2019 at 7:12 PM, CharonY said:

That looks weird. From what I understand you have a tissue strip of a fixed size (and therefore weight) and load it with ethanol at a given percentage. I do not understand why the Evolon (if that refers to the strip) then changes in weight. Intuitively I would have assumed that you would soak the tissue with 51% and 34%, ethanol, respectively. I can only speculate, but is it possible that the did just that and the weight difference is because the cut strips had the respective weight differences (i.e. 92 vs 87 mg) and they tried to account the total ethanol content for that (the numbers still seem a little bit off, maybe someone else has a better idea)?

 

On 11/4/2019 at 7:35 PM, Sensei said:

I am guessing 34% and 51% means concentration of ethanol mixed with water (or other solvent) by volume..

Density of pure ethanol is ~0.789 g/mL so:

102.7 mg / 0.79 g/mL = 0.1027 g / 0.79 g/mL = ~0.13 mL of ethanol by volume

149.1 mg / 0.79 g/mL = 0.1491 g / 0.79 g/mL = ~0.188 mL of ethanol by volume

34% of ethanol and 66% of water/solvent will have total volume 0.13/0.34 = ~0.37 mL

51% of ethanol and 49% of water/solvent will have total volume 0.188/0.51 = ~0.37 mL. So they matches.

 

 

The article can be downloaded from this link: 
https://www.researchgate.net/publication/333190051_Solvent-mediated_extraction_of_fatty_acids_in_bilayer_oil_paint_models_a_comparative_analysis_of_solvent_application_methods
The description is on page 3 under "Simulated cleaning test procedure"

I agree that it looks weird. It could be that they are simply referring to 34% and 51% of ethanol in water and not some weight/weight ratio between Evolon and ethanol. I partly came to that conclusion myself but couldn't seem to get the numbers to match. Could it be that the weights listed for Evolon and ethanol are the weights of the individual Evolon strips and the amount of ethanol absorbed into the tissue? 

So, if I were to try this procedure myself I could soak Evolon tissue in an unspecified amount of ethanol as long as it is 34% or 51%?

Thank you for your replies so far!