Platinum Labware Care and Use Guide

ARTICLE Platinum labware care and use guide

Introduction Care and use The unique properties of platinum have made it a vital Platinum ware can be heated in many atmospheres part of all modern analytical laboratories. Its exceptional commonly employed for laboratory experimentation chemical inertness and ability to tolerate high service such as: temperatures makes it an essential tool in achieving the highest levels of accuracy and reproducibility in • Air, nitrogen and oxygen chemical analysis. • Oxides of nitrogen • Bromine and iodine vapors When properly used and cared for, platinum will outperform and provide a service life unrivalled by any other labware • Hydrogen material. Handled in an incorrect manner, platinum labware • Carbon dioxide. can quickly become useless. Platinum ware is suitable for numerous chemical research To maximise the life and get the most out of your applications such as ignitions, fusions, evaporations and investment, we’ve outlined some basic guides for the use glass production. These are usually accomplished in of platinum labaware. Refer to these simple guidelines to oxidizing atmospheres. extend the life of your labware and keep it on top form. Alfa Aesar offers a crucible cleaning kit containing all of the materials needed to safely clean most types of crucibles.

For Research Use Only. Not for use in diagnostic procedures. © 2016 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries unless otherwise specified.

Art_PlatinumLabwareCareAndUseGuide_2016 Oxides not readily reducible include Al2O3, MgO, BaO, material should come in contact only with platinum or a CaO, SrO, TiO , ZrO , ThO , MoO , WO , Ta O, Cr O , clean refractory. Commonly used fusion agents affect Stock Description Qty 2 2 2 3 3 2 2 3 No. Mn3O4, and in the absence of carbonaceous matter, ZnO, platinum in the following manner: 37995 Cleaning Kit for Laboratory Crucibles 1 each Co3O4, NiO, CdO. • Sodium carbonate. When sodium carbonate is employed, the loss of weight of the platinum amounts to In addition, platinum has characteristics that make it The moist filter paper containing the precipitate is dried in only a fraction of a milligram. exceptionally qualified for electrolytic usage in the a platinum crucible or dish by preheating on a hot plate or laboratory. In the construction of electrodes, platinum suitable gauze over a gas burner. After drying, the dish is • Sodium carbonate mixed with sodium nitrate or nitrite. provides an excellent combination of electrical conductivity, transferred to the area in front of the hot open muffle of a Nitrates or nitrites in the fusion mixture cause heavier losses of platinum than sodium carbonate by itself, but mechanical strength and resistance to electrolytic and furnace operating at 800°C. Within 10 to 15 minutes, the the losses are not likely to exceed one or two milligrams chemical attack. Both cathode and anode remain constant paper will becomes completely charred. under ordinary laboratory conditions. in weight during electrolysis, and deposits can be easily • Sodium borate or sodium metaphosphate. Platinum is dissolved after weighing without damage to the electrodes. The dish should then be placed about two inches inside unaffected by borax at low temperatures. Sodium the muffle where it should remain until nearly all the metaphosphate attacks the metal only at very high Platinum laboratory ware can provide numerous carbonaceous matter has been burned off. The removal of temperatures or under reducing conditions. advantages when properly employed. Some of the basic the last traces of carbon and the decomposition of the • Alkali bifluorides. When alkali bifluorides are used, the guidelines for use in various applications are outlined here. precipitate may require a somewhat higher temperature. loss of weight of the platinum is practically null. This can be applied without detriment to the platinum, • Alkali chlorides or alkali earth chlorides. Both attack providing that reducing conditions are avoided. Free Operating temperatures platinum above 1000°C in the presence of air which The following maximum operating temperatures are access to recirculating air is recommended. Where a liberates chlorine from the fused salt. In a neutral recommended for all applications. suitable care is exercised to assure safety, such atmosphere, these chlorides are inert. precipitates as MgNH PO , MgNH AsO and CaWO may 4 4 4 4 4 • Alkali bisulfates. When alkali bisulfates are involved, Material Temp be ignited. platinum is attacked slightly above 700°C. The attack can Platinum 1400°C be diminished by adding ammonium sulfate. ZGS Platinum 1500°C Determination of ash in organic material Platinum 10% Rhodium 1550°C A shallow dish should be used, and the contents heated ZGS Platinum 10% Rhodium 1600°C well forward in a hot open muffle until combustion is nearly Platinum 5% Gold 1300°C complete. Combustion can be accelerated if the surface is ZGS Platinum 5% Gold 1400°C disturbed from time to time. After all carbonaceous matter has burnt away, final combustion can be conducted in the Ignitions hot zone of the muffle. Platinum ware is widely used for ignitions. Although platinum is subject to attack during ignition by an easily Determination of volatile material in fuels reducible substance, the risk of damage can be avoided by Particular care should be exercised in this operation. In as taking proper precautions in accord with the materials much as it is essential that a nonoxidizing atmosphere can involved. be maintained in the crucible to prevent loss of free carbon, there is danger of contamination of the platinum dish. This Ignition of filtered precipitates is particularly true if the fuel is rich in sulfur or phosphorous Platinum laboratory ware can be utilized in ignitions of the compounds. following precipitates: Fusions • Barium sulfate Fusions in platinum ware should always be performed • Alkaline earth carbonates, oxalates, etc. under oxidizing conditions, using materials that are free from organic substances. During fusions and cooling, the • Sulfates of metals not readily reducible.

Art_PlatinumLabwareCareAndUseGuide_2016 Oxides not readily reducible include Al2O3, MgO, BaO, material should come in contact only with platinum or a Electrolytic operations

CaO, SrO, TiO2, ZrO2, ThO2, MoO3, WO3, Ta2O, Cr2O3, clean refractory. Commonly used fusion agents affect Electrochemical methods of analysis have been widely

Mn3O4, and in the absence of carbonaceous matter, ZnO, platinum in the following manner: adopted because of their speed, simplicity and economy. In

Co3O4, NiO, CdO. multiple analyses of a routine nature such as the • Sodium carbonate. When sodium carbonate is determination of copper in brasses and aluminum alloys, employed, the loss of weight of the platinum amounts to The moist filter paper containing the precipitate is dried in several solutions can be electrolyzed simultaneously. In only a fraction of a milligram. a platinum crucible or dish by preheating on a hot plate or single determinations, the analyst can attend other suitable gauze over a gas burner. After drying, the dish is • Sodium carbonate mixed with sodium nitrate or nitrite. operations while electrolysis is in progress. transferred to the area in front of the hot open muffle of a Nitrates or nitrites in the fusion mixture cause heavier losses of platinum than sodium carbonate by itself, but furnace operating at 800°C. Within 10 to 15 minutes, the the losses are not likely to exceed one or two milligrams Platinum electrodes can be used to advantage in numerous paper will becomes completely charred. under ordinary laboratory conditions. applications: • Sodium borate or sodium metaphosphate. Platinum is • As anodes in most electrolytes except strongly acid The dish should then be placed about two inches inside unaffected by borax at low temperatures. Sodium chlorine solutions. the muffle where it should remain until nearly all the metaphosphate attacks the metal only at very high • As cathodes for the deposition of metals from acid, carbonaceous matter has been burned off. The removal of temperatures or under reducing conditions. alkaline or ammoniacal solutions. For the deposition of the last traces of carbon and the decomposition of the • Alkali bifluorides. When alkali bifluorides are used, the zinc, gallium and bismuth, the platinum should first be precipitate may require a somewhat higher temperature. loss of weight of the platinum is practically null. copper-plated to prevent superficial alloying with the This can be applied without detriment to the platinum, deposited metal. • Alkali chlorides or alkali earth chlorides. Both attack providing that reducing conditions are avoided. Free platinum above 1000°C in the presence of air which access to recirculating air is recommended. Where a liberates chlorine from the fused salt. In a neutral Glass production suitable care is exercised to assure safety, such atmosphere, these chlorides are inert. When producing glass in a platinum alloy vessel, all batch precipitates as MgNH PO , MgNH AsO and CaWO may materials must be fully oxidized and silica-bearing refractory 4 4 4 4 4 • Alkali bisulfates. When alkali bisulfates are involved, be ignited. platinum is attacked slightly above 700°C. The attack can materials must be avoided in order to ensure long vessel be diminished by adding ammonium sulfate. life. When cleaning the vessel to remove glass residue, soak Determination of ash in organic material in 50% hydrofluoric acid at no more than 180°F. Do not A shallow dish should be used, and the contents heated When any of the previous fusion agents (except alkali allow hydrofluoric acid to boil. This process may take well forward in a hot open muffle until combustion is nearly bifluorides) are employed, traces of platinum should be several days. To speed up glass removal, occasionally complete. Combustion can be accelerated if the surface is sought in making an accurate analysis. Platinum can be remove the vessel from acid bath and scrub soft glass disturbed from time to time. After all carbonaceous matter precipitated with the hydrogen sulfate group. residue away. Make sure skin is protected; hydrofluoric has burnt away, final combustion can be conducted in the acid will leave serious burns. hot zone of the muffle. Evaporations Platinum laboratory ware can be employed in evaporations Determination of volatile material in fuels containing the following: Particular care should be exercised in this operation. In as much as it is essential that a nonoxidizing atmosphere can • Sulfuric acid with or without hydrofluoric acid be maintained in the crucible to prevent loss of free carbon, • Hydrofluoric acid there is danger of contamination of the platinum dish. This is particularly true if the fuel is rich in sulfur or phosphorous • Hydrofluoric and nitric acid when the halides (especially chlorides) are absent compounds. • Hydrochloric acid in the absence of oxidizing agents that yield nascent chlorine Fusions Fusions in platinum ware should always be performed • Alkali hydroxides or carbonates where contamination of under oxidizing conditions, using materials that are free the solution with silica must be avoided from organic substances. During fusions and cooling, the • Sodium peroxide solutions.

Art_PlatinumLabwareCareAndUseGuide_2016 Conditions to avoid when using platinum labware and Solids (including their fusions and vapors) platinum fabricated products • Sulfur, selenium and tellurium: The action of sulfur vapor is very slow and prolonged heating is required to produce When heated, platinum can be attacked by certain any serious effects. Selenium and tellurium combine atmospheres, solids, fusions and vapors. The following readily with platinum. should be avoided, as noted, when high temperatures • Phosphorus, arsenic and antimony: Combine with (greater than 1000°C) are involved: platinum readily.

Atmospheres • Magnesium pyrophosphate: Harmful above 900°C. • Ammonia: Darkens the surface and makes it less • Silica and borax: Harmful at high temperatures. lustrous. In time, it will develop pores and create a crystalline appearance. • Molten lead, zinc, tin, bismuth, silver, gold or copper, or mixtures that form these metals by reduction. All combine • Sulfur dioxide: Promotes the formation of sulfur trioxide. readily with platinum to form a lower melting point As a result, the platinum surface is coated with platinum sulfide. eutectic alloy. • Chlorine: Converts the metal into a mass of crystals • Fused alkali oxides and peroxides, to a lesser degree in because of the alternate formation and decomposition of the presence of air, alkali hydroxides. platinous chloride. • Fused nitrates: The action is intensified by the presence • Volatile chlorides: Especially those that decompose readily. of alkali hydroxides or carbonates, but is not severe in any case. • Highly carburetted gases and vapors: They aggressively • Fused cyanides: Plantinocyanides are formed. attack the metal with the possible formation of PtC and make it very brittle. Hence, platinum ware should never be • Iron oxide above 1200°C: At this temperature, oxygen is heated in the reducing zone of a gas flame. liberated and the iron combines with the platinum. • Silica, silicates, alumina and magnesia above 1600°C: At Liquids lower temperatures, no action occurs. • Aqua regia. • Fused alkali and alkali chlorides in the presence of air at • Hydrochloric acid and oxidizing agents. 1000°C or above. • Concentrated sulfuric acid: It is harmful when extended • Lead and bismuth oxides above 1250°C. periods are involved. In most laboratory applications, the action is so slow that it is usually negligible. • Concentrated phosphoric acid: The action is noticeable only after prolonged heating.

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