ethyl alcohol table

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Hello guys. I have a doubt. I have to extrapolate from the table USP title.
You know what is the calculation to apply when I do not have the precise density indicated in the table? thank you all

Linear interpolation. *Any* relationship is approximately linear if you look at a narrow enough range, and your table is in 1% increments by weight.
-- Tom Jupille
LC Resources / Separation Science Associates
+ 1 (925) 297-5374
Is your problem that you have a density or specific gravity that is lower or higher than on the chart, or that you have few significant digits? If it is a digit issue then you're answer will most likely need to have some error associated with it.
I have a list (AOAC 1990 Percentages by volume at 15.56C) that goes from 0% all the way to 99.98% If you let me know what specific gravity you have I can give you the Ethanol content

HI!! My density is 0.807

crimelist wrote:
HI!! My density is 0.807


Seek and ye shall find;

NB NB that density is meaningless without temperature.

Peter Apps
Right... 0.807 (@25°C)
at 0.807(25C) your percent Ethyl alcohol should be 95.56%

Remember that these tables are for mixtures of ethanol and water ONLY, so one needs to make that assumption too.
Remember also that "percent Ethyl alcohol" could be mass/mass or volume/volume (and a few other less likely ones).

Peter Apps
Peter Apps wrote:
Remember also that "percent Ethyl alcohol" could be mass/mass or volume/volume (and a few other less likely ones).

In USA, ethyl alcohol percent is almost always expressed in volume/volume, likely a smoke and mirrors thing with alcoholic beverages to obtain a "higher number". So even consumer products like hand sanitizer gels are always listed for alcohol content as volume/volume.

Now, when I assayed competitive products that contained low levels of ethyl alcohol (such as Tide or Persil laundry detergents), then I reported those results as weight/weight percent as customer wanted.
Thank you. It is possibile to calculate with an excel file ?
Yes, you can do it with Excel.

No, nobody here is going to do it for you.

Peter Apps
Of course.... I do.

But I need a help for formula :)
USP in it's stimuli article has given the formula for extrapolation of specific gravity at 25°C to 15.56°C as below.

Extrapolated Value = R U1 – [( R T1 – S) × ( R U1 – R U2 )/( R T1 – R T2 )]
R T1 = Upper value of the test range
R T2 = Lower value of the test range
R U1 = Upper value of the unknown range
R U2 = Lower value of the unknown range
S = Experimental value

Specific Gravity (SG) for Alcohol determined at 25 converted to 15.56

Sample SG = 0.7893 at 25 .
From the table select the 25 and corresponding 15.56 range for your result:
25 (test range)
15.56 (unknown range)

0.7921 0.7986
0.7871 0.7936

R T1 – R T2 = 0.7921– 0.7871 = 0.0050
R U1 – R U2 = 0.7986 – 0.7936 = 0.0050
0.7986 – [(0.7921 – 0.7893) × 0.0050/0.0050] = 0.7958 SG at 15.56°C.

I was referrring to dehydrated alcohol USP spec. when came across this calculation. There are still two questions unanswered.

1. How to calculate the alcohol strength by referring to alcoholometric table?
2. What to do if the specific gravity is below the highest value in the table. Then the above formula does not apply.

I have searches a lot on the net but could not get any suitable answer. Can anyone help????
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