An introduction to
Lead Nitrate

There is evidence that man has
extracted and used lead for over 6,000
years. More recently the Ancient
Romans used lead to make pipes for
plumbing (a word derived from the
Latin word for lead) and vessels for
wine and food processing and storage.

Alchemy is the ancient practice of
trying to turn base metals into gold.
Lead was the first and oldest of the
seven classical metals of alchemy
(others were gold, silver, mercury,
copper, iron & tin).

The symbol on the right is the
alchemical symbol for lead.
Lead in history

Lead is a metallic element with the symbol
Pb (Latin: plumbum) and has Atomic No.
82. It is dense (11.3g/ml) and has a
relatively low melting point (327˚C).

It is one of the toxic “heavy metals” and
has no biological use at all.

As a metal lead is soft, highly malleable
and ductile. It has a bluish-white colour
when freshly cut, but tarnishes to a dull
greyish colour when exposed to air.
However, it is relatively corrosion resistant
(e.g. lead sinkers last in sea water for very
long periods).

Lead provides a very good shield against
radiation and is widely used for this
purpose
Lead metal

The major use for lead is the manufacture of batteries.
The use of lead in ammunition is also widespread. A
range of lead compounds are used in other
applications but besides for making batteries lead use
is in decline.

Nevertheless world consumption and production of
lead continues to rise and is around 8 million tonnes
per year. A little over half the world’s lead
requirement is met by recycling of lead products
(mainly batteries).

Globally around 3.9 million tonnes of lead is mined
annually. Australia is the world’s biggest lead miner
(mostly in combination with zinc at mines such as
Cannington, MacArthur River, Century and Mt Isa).
Lead Metal

Lead reacts with other elements and compounds to form a
wide range of compounds. Examples are: lead acetate,
lead carbonate, lead chloride, lead chlorate, lead chromate,
lead hydroxide, lead iodide, lead nitrate, lead oxalate, lead
oxide (litharge), lead sulphate, lead sulphide (=galena, the
most common lead ore) and tetra-ethyl lead (formerly
used as an anti-knock compound in petrol) .

Most lead compounds have very low solubility in water with
3 exceptions – lead acetate, lead chlorate and lead nitrate.

Of these water soluble lead compounds lead chlorate is too
reactive for safe handling while lead nitrate has a higher
lead content, higher solubility and is a less expensive
compound than lead acetate which is why it is the most
commonly used source of lead for gold leaching.
Lead compounds
Lead nitrate is a very stable inorganic compound with:

Molecular Formula:
Pb(NO3)2

Molar Mass:
331.2 g/mol

Solubility in Water:
52 g/100 mL (20 °C)

Structural Formula:
Chemical properties

Lead nitrate does not occur naturally and is usually
produced by means of the following reaction:
3 Pb
lead metal
+
8 HNO3
nitric acid
3 Pb(NO3)2 + 2 NO  + 4H2O
lead nitrate
nitric oxide (gas)
Lead feedstock can be in form of ingots, lead shot or
scrap such as battery electrodes. Very occasionally
other lead compounds are reacted with nitric acid.
Manufacture of Lead Nitrate

The final stage of most lead nitrate
manufacturing processes is the
recovery of the lead nitrate from
the reaction mix in the form of fine
crystals.

The crystalline material is the most
convenient form that can be packed
for shipping and storage.

Dry lead nitrate is classified as
Dangerous Goods with its own UN.
No 1469 and is in both UN DG Class
5.1 “Oxidising agent” and also UN
DG Sub-Class 6 “Toxic”.
Lead nitrate crystal

Lead nitrate has been made on a relatively small scale since the
Middle Ages, predominately as an intermediate in the manufacture
of pigments for paints and dyes and later in pyrotechnics.

The use of lead nitrate in the manufacture of paints and fireworks
has greatly declined because of greater recognition of lead’s
hazardous nature, but current industrial applications include: as a
stabiliser in nylon, polyester and other plastics, as a coating for
photothermographic paper, and in gold mining.

In gold mines lead nitrate was commonly added to activate the zinc
dust used in the Merrill-Crowe gold recovery process, which has now
mostly been replaced by CIP/CIL.

The benefit of lead as a leach enhancer in gold cyanidation has been
recognised since the early 80s but it has only been since the mid90s that the use of lead nitrate as a lead source has become
widespread in gold cyanidation to improve leaching kinetics and
increase the quantity of gold recovered from sulphide ores.
Lead nitrate applications

Lead nitrate solution is supplied at a concentration
of 40%w/v.

The specific gravity of the solution is 1.33

The natural colour of the solution is clear but a yellow dye
is added to make it more visible.

Each delivery is approximately 16.8kl in volume. Transfer
of the solution into the site storage tank is carried out by
the delivery driver.

The solution is classified as Dangerous Goods. It has UN
DG No. 3122 “Toxic liquid, oxidising N.O.S.” and is in both
Class 6 “Toxic” and in DG Sub-Class 5.1 “Oxidising agent”
Lead nitrate solution

The key safety requirement when working with lead nitrate
or any other lead compounds is to prevent any lead from
entering the body.

Lead is able to enter the body by the following means:
 Inhalation of dusts and vapours
 Swallowing
 Skin contact

As supply of lead nitrate to mine sites is in the form of
solution transferred directly into the on-site bulk storage
tank, each of these risks is minimised.
Safety

In the dry form lead nitrate is relatively dense and is not very
dusty but can still represent a significant inhalation risk.
However this risk is largely eliminated when the lead nitrate is
inx solution, which under most conditions has a minimal
inhalation risk.

The lead nitrate solution is not at all volatile. Any evaporation
from the surface of the solution will be in the form of pure
water vapour only.

If lead nitrate solution is allowed to dry out (which usually
occurs on any surface exposed to the atmosphere) a dry lead
nitrate residue will start to form as the water evaporates. It is
therefore important that any spills or leaks of the solution are
rinsed away and the rinse water is transferred to a leach tank
or to tailings.

The delivery driver rinses away any drips, spills or splashes
that occur during deliveries.
Inhalation Risk

There is the potential for a lead nitrate-containing mist to
form if lead nitrate solution is under pressure and is then able
to escape as a spray from any small apertures in a pump,
delivery transfer line or dosing line.
To prevent the above hazard the transfer line used for
deliveries is regularly pressure tested.
It is also recommended that the lead nitrate dosing line
conveying the lead nitrate from the storage tank to the dosing
point be periodically pressure tested to check for the presence
of holes or leaks.

Lead nitrate is an oxidising agent but while it remains in
solution it would have a very limited effect as an oxidiser. If
there were a fire hot enough to crystallise lead nitrate from
the solution these crystals would act as oxidising agents and
assist combustion. Dry lead nitrate in contact with a fire could
decompose to yield lead-containing vapours so a self
contained breathing apparatus would be required to protect
for personnel dealing with such a fire.
Inhalation Risk II

Given the storage and handling arrangements at mine sites
the ingestion of lead nitrate by swallowing would be an
extremely unlikely occurrence.

Whenever there is a requirement for an operator or
maintenance person to work on the lead nitrate storage or
dosing system they should wear the correct PPE to avoid any
direct contact with the solution. As far as is practical any
equipment in contact with lead nitrate solution should be
thoroughly rinsed with potable water before the work begins.

After working in contact with any of the lead nitrate
equipment the PPE used should be thoroughly rinsed.

Following the removal of the PPE the personnel involved
should always wash hands, faces, necks and arms.

No eating, drinking or smoking should be permitted in the
vicinity of the lead nitrate storage or dosing areas.
Swallowing

Lead nitrate and most other forms of lead can be absorbed
if in direct contact with the skin.

The correct use of PPE will prevent direct skin contact with
lead nitrate solution or dried lead nitrate residues left after
evaporation of the water from solution released by spills or
leaks.

In the event that lead nitrate in any form were to come
into contact with the skin it should immediately be rinsed
off using potable water.

Any lead nitrate contaminated clothing must be
immediately removed for washing separately from other
garments.
Skin Absorption

Because of its toxicity lead nitrate solution must be
prevented from spilling on to bare earth.

As the delivery, storage and dosing of the solution at mine
sites takes place within bunded areas the spill hazard is
well contained.

Once the lead nitrate is added to the ore slurry it quickly
becomes dispersed and the lead is diluted down to very low
concentrations.

In contact with the many anions present in the ore slurry
all of the lead nitrate is changed into insoluble lead
compounds which effectively locks up the lead and
prevents leaching of the added lead from the tailings dams.
Lead and the environment

Lead is a toxic element and must be kept out of the body

The bulk lead nitrate solution storage and handling facilities
installed at mine sites provide optimum conditions for the
safe handling of the solution

Whenever work needs to be done on the lead nitrate
handling equipment at mine sites the correct PPE must be
used to prevent direct contact with the solution.

Good hygiene practices must be observed following any
work carried out in areas where contact with the lead
nitrate solution could have occurred.
Conclusion