The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Nitric Acid percent to specific gravity

I am looking for the conversion factor to convert percentages of Nitric Acid to Specific Gravity. I understand that the conversion is temperature dependent.

Lisa Grosskopf
project/quality engineer medical devices - Ontario, California, USA
2004

---

2004

You can find that data in any good handbook, like Lange's Handbook of Chemistry [adv: on Amazon, AbeBooks, or eBay affil links] or the CRC Handbook of Chemistry & Physics [adv: on Amazon & AbeBooks & eBay affil links] . It is also in some engineering handbooks and in some ASM books. Your vendor may be able to supply it also. At a last resort, you can make a number of % solutions, take the specific gravity of each and plot the % against SG. To be more precise, you might need to titrate each solution. % is somewhat questionable as you must define the starting acid. No one is going to do much work with fuming red nitric acid which is the strongest commercially available nitric. Normally it is sold in a diluted form (by baumé) which can be converted to SG.

James Watts
- Navarre, Florida

---

2004

Since the relationship between the WEIGHT percentage and specific gravity is slightly non-linear, there is no numerical factor that can be used. However, here are a few points that you could plot to get a curve, with the WEIGHT percentage 1st and the SG 2nd, all at 20 degrees C (68 deg F): (5.00,1.0276),(10.00,1.0562), (15.00,1.0859), (20.00,1.1170), (30.00,1.1822), (40.00,1.2489). This data is from the CRC Handbook of Chemistry and Physics.

On a more practical level, you would be better off setting this up on a VOLUME percentage basis, based on the strength of the particular nitric acid being used. The simplest and most accurate way of doing this may be to get some nitric and water, make several mixes, determine their SG's, and, finally, make a graph. You can tare an empty volumetric flask, pipet in the nitric, add water to the mark, weigh in grams, and divide by the size of the vol flask, in order to get the SG's. Repeat with various amounts of nitric until you get a good working curve.

Chris Owen
Consultant - Houston, Texas

---

2004

I've used regression to obtain the following relationships,

Conc(%) = (0.0012*T*T + 0.1668*T + 49.954)*(4.3607*sg*sg - 8.3149*sg + 4.328245)

T in degC in range 0 - 70, sg in range 1.3 - 1.36. Conc(%) seems accurate for the range 50 - 60. I realize this equation is not based on any physical laws (I'm not sure there is one for Nitric Acid). Use at own risk.

Malcolm Boczek
- Courtright, Ontario, Canada