Hydrochloric acid

Legality: DEA Listed Chemicals

Production of this substance may be illegal in some jurisdictions under certain circumstances.

21CFR1310.02 a & b

In 1995/6, two lists were created "List I" and "List II", for which commercial manufacturers and distributors must register, and for which possession with the intent to manufacture illegal substances (such as methamphetamine, ecstasy, etc) is illegal. On these a few dozen "precursor" compounds commonly used in the manufacture of illegal drugs.

Bottom line: Do not produce this chemical without checking to make sure that you may do so legally.

 

 

Hydrochloric acid
DEA LIST I/II SUBSTANCE

Chemical formula	HCl(aq)
Water azeotrope(%w/w)	20.2%
Water azeotrope bp(°C)	110
NFPA 704	0 3 1 ACID

Hydrochloric acid is a solution of hydrogen chloride dissolved in water.

Uses

• Industrial chemical
• Chlorination
• Feedstock for aqua regia

Natural occurrence

• Hydrochloric acid is produced in the human stomach.

Hazards

• Extremely corrosive, reactive with many metals.

Character

Concentration			Density		Acidity		Viscosity	Specific heat	Vapor pressure	Boiling point	Melting point
Molarity	%w/w	g/L	Baumé	sg.	pH	pKa	mPa·s	kJ/(kg·K)	kPa	°C	°C
2.87	10%	104.80	6.6	1.048	−0.5		1.16	3.47	1.95	103	−18
6.02	20%	219.60	13	1.098	−0.8		1.37	2.99	1.40	108	−59
	20.2% (az)									110
9.45	30%	344.70	19	1.149	−1.0		1.70	2.60	2.13	90	−52
10.17	32%	370.88	20	1.159	−1.0		1.80	2.55	3.73	84	−43
10.90	34%	397.46	21	1.169	−1.0		1.90	2.50	7.24	71	−36
11.64	36%	424.44	22	1.179	−1.1		1.99	2.46	14.5	61	−30
12.39	38%	451.82	23	1.189	−1.1		2.10	2.43	28.3	48	−26
The reference temperature and pressure for the above table are 20 °C and 101.325 kPa. Vapor pressure values are taken from the International Critical Tables and refer to the total vapor pressure of the solution.

Production

Synthesis

via sulfuric acid

Combine concentrated sulfuric acid with salt, yielding hydrogen chloride and sodium bisulfate and/or sodium sulfate. The first is favored energetically, so if the chemicals are available in (near) that ratio, the bisulfate will be produced.

H₂SO₄ + NaCl → NaHSO₄ + HCl

H₂SO₄ + 2 NaCl → Na₂SO₄ + 2 HCl

via sodium bisulfate

Dry distill sodium bisulfate and salt, producing sodium sulfate and hydrogen chloride gas

NaHSO₄(s) + NaCl(s)

{

→

heat}

Na₂SO₄(s) + HCl(g)

via phosphoric acid

H₃PO₄(l) + NaCl(s)

{

→

105°C}

NaH₂PO₄(s) + HCl(g)

via chloralkali

Main: Chloralkali process

Membrane electrolysis of aqueous sodium chloride:

NaCl + H₂O → NaOH + HCl

Purification

Azeotropic distillation at 108.6°C, giving 20.2%w/w HCl. This azeotrope is removed completely by adding 25% by weight calcium chloride, allowing the HCl to be boiled off the water in its entirety. The remaining water can be boiled dry to recycle the CuCl₂.

Disposal

Neutralize with sodium carbonate or calcium carbonate

Na₂CO₃ + 2 HCl → 2 NaCl + CO₂ + H₂O

CaCO₃ + 2 HCl → CaCl₂ + CO₂ + H₂O

See Also

• Hydrogen chloride
• Chlorine
• Mineral acid intraconversion