GOLD ANNEALING CRUCIBLES, PARTING AND ANNEALING QUARTZ CRUCIBLES AND PARTING FLASKS

After cupellation, we obtain a bead made of gold and silver. Therefore, it is still necessary to separate the silver from the gold. To achieve this,  we attack two times the bead with boiling nitric acid and then we anneal it. This process is called “parting” and “annealing”. Gold annealing crucibles and parting flasks are the key instruments to achieve this.

The reason for using nitric acid, is that silver is soluble in it but gold is not.  However, to ensure that no silver is secluded into the gold, and therefore protected from being dissolved, it is first necessary to laminate the bead into a cornet.

It is possible to do the nitric acid attack in quartz parting and annealing crucibles or in borosilicate parting flasks. Quartz parting and annealing crucibles have the advantage of requiring less manipulation of the bead because the next step of the process  (gold annealing) is done using this same crucible. 

After the nitric acid attack, the obtained pure gold cornet is very brittle because it is covered by a multitude of holes left by the dissolved silver. At this point, it would be unsafe to weight the gold cornet due to the risk of breaking it and losing a part of the sample. This is why it is necessary to anneal the gold cornet in a quartz parting and annealing crucible or in a fireclay gold annealing crucible. 

The Annealing process consists of just heating the gold cornet above it recystalization tempearute at 850ºC but without melting it. After annealing the cornet is more “solid” and can be weighted safely withou risk of breaking it.

Fire Assay SL supplies the parting and annealing accessories to achieve this:

 

QUARTZ  PARTING & ANNEALING BASKETS – QUARTZ GOLD ANNEALING CRUCIBLES – Allowed by ISO11426 
Quartz baskets for parting and gold aneealing
Quartz Parting and Annealing Basket
Quartz thimble for parting and annealing
Types of quartz thimbles for parting and annealing

We supply a range of quartz baskets that allow to carry out the successive parting and annealing operations in the same container, and substitute, both parting flasks, and gold annealing crucibles.

These quartz baskets are capable of withstanding:

  • Attack of concentrated nitric acid
  • High temperature necessary for annealing (up to 1000ºC)
  • Thermal shock due to very low coefficient of thermal expansion.

They are therefore suitable for processing samples in parallel during the two nitric acid attacks (the first with nitric acid 33%, the second with nitric acid 49%), and then go directly in the gold annealing furnace (after rincing with water).

On the other hand, we also supply the borosilicate beakers in various sizes to fit the diagonal of the baskets. The beakers are supplied with watch lids or with a chimney to avoid nitric acid spillage at boiling point or to conduct the vapours.

The quartz thimbles are provided with thin slits to evacuate the nitric acid / distilled water and possess a flange at the top to fit the holes of the basket.

It is possible to supply them as spares in case of breakage. There are two types of quartz thimbles / crucibles and they suit most cornet sizes.

The following parting and annealing baskets configurations are available:

Basket
Reference
Dimensions (L x W x H)
(mm)
Capacity
(samples)
Picture
QBR-642x57x706 (2 x 3)Quartz parting & annealing bsket for 6 samples
QBR-1257x72x7012 (3 x 4)
Quartz Parting and annealing basket for 12 samples
QBR-2587x87x7025 (5×5)Quartz Parting and annealing basket for 25 samples
QBR-36102x102x7036 (6×6)Quartz Parting and annealing basket for 36 samples
QBR-49117x117x7049 (7×7)Quartz parting and annealing baskets with 49 thimbles
Quartz partind and gold annealing Baskets

Quartz parting and annealing baskets with beaker and chimney
Quartz parting and annealing baskets with beaker and chimney
Quartz parting & annealing baskets for 49 samples
Quartz parting and annealing baskets with 49 thimbles
Advantages of parting & annealing baskets
CORROSION RESISTANCE

Quartz parting and annealing baskets withstand concentrated boiling nitric acid.

Cornets travel untouched through parting / rinsing / annealing.

Assays keep original array – no misplace errors

TEMPERATURE RESISTANCE

Quartz parting and annealing baskets  resist temperatures up to 1000ºC.

Furthermore, quartz has an extremely low thermal expansion coefficient (5.5×10−7/°C ; 20–320°C).  This allows our parting and annealing baskets to resist rapid and large temperature changes without cracking (they have a great resistance to thermal shock).

EFFICIENY IMPROVEMENT IN OPERATIONS

Quartz parting and annealing baskets allow full scalability to mass analysis production stage.

Extends inherent parallel processing capabilities of Fire Assay.

Save time and reduce manipulation hazards.

ECONOMIC SAVINGS

Quartz parting and annealing baskets  save Labour, Reagents (HNO3 – H2O), Reduced Energy consumption.

BOROSILICATE GLASS PARTING FLASKS
Fire Assay / Cupellation Borosilicate parting flasks
Parting Flask

Parting Flask made with low thermal expansion borosilicate glass withstands both nitric acid attack and thermal shock.

Additionally, they have a tall narrow neck designed to fit inside gold annealing cups.

Finally, the dimensions of our parting flasks are: 230 x Ø 48 x Ø 18

FIRECLAY CUPS – GOLD ANNEALING CRUCIBLES
Gold annealing crucibles
Gold Annealing Crucibles
Gold annealing crucibles on tray P51
Gold annealing crucibles on tray P51

Fireclay Annealing Cups / gold annealing crucibles possess a smooth unglazed surface and thin walls that provide them with excellent resistance against thermal shock.

Furthermore, they have a tronco-conical form designed for gold bead annealing and for ignition of precipitates such a barium sulphate and copper sulphide.

ReferenceHeightDIameterPicture
CORNET ANNEALING CUPS nº 2272525Gold annealing crucibles 25 x 25
CORNET ANNEALING CUPS nº 2303230Gold Annealing Crucibles 30 x 32
CORNET ANNEALING CUPS nº 2313334Gold annealing crucibles 34 x 33
Gold Annealing Crucibles