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Determining Nitric Acid Strength

Nitric acid is highly corrosive and is also an oxidizer. When nitric acid reacts with water, it also generates heat.

Why sample Nitric Acid?

  • To ensure acid strength and purity

What to Look for in the Sample

  • Acid Strength
  • Sulfates & Chlorides (Spectrophotometric Method)
  • Fluorides (Ion Electrode Method)
  • Iron (Inductively Coupled Plasma (ICP) Spectroscopy)

How to Safely Take Nitric Acid Samples

  • BIAR Multi-Function 304L or PFA-lined inline sample valve with spring-to-close function
  • Thread Adapter or Bottle Support
  • Safety Cabinet (vented)
  • Safety Plug (for secondary containment)
  • Use open containers such as plastic bottles

Because nitric acid is extremely corrosive, 304L stainless steel or PFA-lined sample valves are considered a better option due to their low carbon content and corrosion resistance to nitric acid.

A BIAR inline sample valve with a thread adapter allows the bottle to be screwed directly onto the valve and allows the fumes to be vented away from the operator with a vent connection at the back of the valve. This feature also prevents the buildup of pressure inside the bottle.

Given the fact that nitric acid fumes are dangerous, it is useful to have a suitably vented safety box to reduce the risk of operator exposure.

Nitric Acid

1) Description

Name: ..............................................................................................Nitric Acid

Chemical Formula: .....................................................................HNO3

CAS No: ..........................................................................................7697-37-2

Other Names: ...............................................................................aqua fortis, hydrogen nitrate, red fuming nitric acid, white fuming nitric acid, engraver’s acid.

Uses: ...............................................................................................Industrial

Physical state: ..............................................................................Liquid

Color: ..............................................................................................Colorless, yellow, or red, fuming liquid

Odor: ...............................................................................................Acrid odor

Boiling Point: ................................................................................83°C (181°F)

Melting Point: ...............................................................................-41°C (-44°F)

Flammability (solid, gas): ..........................................................N/A

2) Hazards

Nitric Acid is considered Immediately Dangerous to Life or Health (IDLH) by Niosh (1994).

Noncombustible Liquid, but increases the flammability of combustible materials.

H272: May intensify fire; oxidizer.
H290: May be corrosive to metals.
H314: Causes severe skin burns and eye damage.
H318: Causes serious eye damage.
H330: Fatal if inhaled.
H370: Causes damage to organs.
H372: Causes damage to organs through prolonged or repeated exposure.
 

Reactivity: Combustible materials, metallic powders, hydrogen sulfide, carbides, alcohols Note: Reacts with water to produce heat. Corrosive to metals.(NIOSH)

Specific Hazards related to Sampling: Nitric acid is extremely corrosive and can cause severe burns. It can be sampled into a bottle, but nitric acid mists are also highly dangerous and fumes must be kept away from the operator using a good ventilation system.

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Nitric Acid Factsheet_Page_2_Image_0001

3) Sampling Facts

a) Why plants need to sample

Plants need to verify the strength of the acid as it is produced in varying strengths.

b) What are they looking for/measuring in the sample

Acid strength on a regular basis.

More stringent tests for:

Sulphates: Spectrophotometric Method

Chlorides: Spectrophotometric Method

Fluorides: Ion Electrode Method

Iron: ICP (Inductively Coupled Plasma) Spectroscopy

 

4) Most common Sample Receptacles

Nitric Acid is sampled into open-top containers such as plastic bottles.

 

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