Specific Gravity Question - Chemists Corner

Formulating

Specific Gravity Question

Posted by ledude on October 17, 2014 at 9:47 am

We are buying raw material (liquid emulsion) from a supplier and think we are getting shorted on our purchases.

I took a specific gravity reading of the material using a gardco weight per gallon cup and found the material to be almost 1.00g/ml.

However, the supplier is claiming that a 55-gallon drum of material only weighs 441 lbs? If the specific gravity is 1.00, shouldn’t the material weigh 459 lbs if filled full?

Thanks for any input!

belassi replied 9 years, 10 months ago 2 Members · 3 Replies
3 Replies

belassi

Member
October 17, 2014 at 11:52 am

441 compared with 459 is a 4% error. I really doubt that you can measure that accurately using your measurement technique. This issue is made much more complex by your use of ancient units. The US gallon is different to the Imperial gallon even! This is why we should work only in metric when formulating.

55 US gallons = 208.197L

441 pounds = 200.03Kg

density = 0.961

Which sounds about right for a w/o emulsion.

Since it is an emulsion the density can never equal 1 because oils have a typical density of around 0.9

Measuring using cups or similar is hopelessly inaccurate.
ledude

Member
October 18, 2014 at 5:58 pm

Thank you for your reply. Let me before clear then. I measured 100ml of the emulsion and it weighed 99.96 grams. Therefore it is logical to assume that the finished product should weigh 458.79 lbs. Yes I realize this is an “ancient” system, but one that is used by most USA manufacturers (where this forum is located) use when selling raw materials.

Also most emulsions are closer to 1.0 as there is more water content than oil…
belassi

Member
October 19, 2014 at 6:19 pm

You can easily get 0.5% error just by the meniscus observation alone. I use a range of graduated cylinders but I would never trust my volume accuracy. I use the scales for everything.

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