Caring & Cleaning of Platinum Labware

Though no doubt platinum offers exceptional resistance to a host of things, but platinum labware is not beyond damage. Platinum lab ware can get damaged by aggressive chemicals or during the evaporation process.

Another way of damage is by the elments forming low melting phases with platinum. So to minimize the chances of damage a proper plan needs to be in place for handling or caring of the platinum labware. Some of this damage avoiding techniques are discussed here.

There should be total avoidance of prolonged heating of platinum if it is not necessary. This promotes the growth of crystals leading to cracks
Only a clean refractory material is to be used for placing of hot platinum labware. Dirty or cold metallic surface should never be used
Situation permitting, a platinum labware should always be heated under oxidizing conditions. If platinum labware is heated over a bunsen burner it is always advisable to use the upper nonluminous cone in place of the inner cone.
For avoiding free carbon which embrittles platinum, a smoky flame should be totally avoided.
Perfectly clean platinum-tipped tongs are to be used while handling hot platinum vessels. If only base metal tongs are available then platinum vessel should be cooled before tongs are used.
A platinum crucible should not be heated if it is in touch with another platinum vessel. This may lead to welding together of the two.
Care should be taken to avoid distortion of the vessels while melts are dislodged from crucibles. In case there is distortion the the crucible should be reshaped.

Operating Temperatures for Platinum Labware
The following table gives the recommended maximum operating temperatures for different Platinum alloys needed for all applications:

Material	Temperature
Platinum	1400°C
Platinum with 10% rhodium	1550°C
Platinum with 5% gold	1300°C
ZGS Platinum	1500°C
ZGS Platinum 10% Rhodium	1600°C
ZGS Platinum 5% Gold	1400°C

Cleaning of Platinum Labware

Cleaning of Dishes and Crucibles : Platinum vessels like crucibles and dishes should be thoroughly cleaned after use. Impurities like organic matter can be removed by immersing them in a chromic acid cleaning mixture. For removing metal oxides or insoluble carbonates boiling in a hydrochloric acid solution is required. This treatment is generally followed with an additional treatment of boiling in nitric acid. Before this is done the article must first be rinsed thoroughly. This rinsing is done to avoid mixing of hydrochloric acid with nitric acid which can damage platinum crucibles and dishes. For removing adherent silica, silicates, metal and also metal oxides, generally the solvent action of fused potassium bisulphate is employed. After fusion takes place, the molten bisulphate is run over the inner surface. Then after cooling the melt is dissolved in boiling water and thoroughly rinsed. Sometimes for supplementing the process, boiling in a hydrochloric acid may also be needed. After cleaning has been done the platinum crucible or dish is generally polished by rubbing with a mild polish.
Cleaning of Electrodes : A platinum electrode after it is removed from the electrolyte is washed with water. A second washing takes place using alcohol. Then it is dried in a stream of warm air at temperatures not more than 100°C. A note of caution, Electrodes should never be dried by a vigorous shaking. This action can bend the stem. Eventually the stem may be fractured by continuous bending and straightening.

Caring for Platinum Labware