1) Borax and then using ultrasonic
2) Some soft solutions, but I don't know exactly what?
It depends on what you used the Pt crucible for. If your crucible contained a silicate glass you can put it in HF and let it clean which it might take some time. Or you can melt Borax or Sodium Metaborate (Na2B2O4) in the crucible (1000-1100˚C) for some time (30-120min) and then use flux (1:1, in weight, mixture of Na2CO3 and K2CO3) melt at 1000˚C for about 15-30min and then either put it in HCl (6M) or HF.
If you used the Pt crucible for other glasses like borate glasses the flux and HCl will do the job!
for the quartz crucible you can use a drops of concentrated HCl . Is it available for cuvettes ? I don't know
It depends on what you used the Pt crucible for. If your crucible contained a silicate glass you can put it in HF and let it clean which it might take some time. Or you can melt Borax or Sodium Metaborate (Na2B2O4) in the crucible (1000-1100˚C) for some time (30-120min) and then use flux (1:1, in weight, mixture of Na2CO3 and K2CO3) melt at 1000˚C for about 15-30min and then either put it in HCl (6M) or HF.
If you used the Pt crucible for other glasses like borate glasses the flux and HCl will do the job!
Following the answer of Ali Mohammadkhah, for HF cleaning, you can accelerate the process by putting the Teflon container in an ultrasonic bath.
Quartz cuvettes can be cleaned using an aquaregia solution which is comonly used in cleaning glass ware ( 3:1 HCl; HNO3)
We use Na2CO3 to clean out Pt crucibles in which we have melted glasses, melted around 1000oC then poured out & repeated as necessary, followed by placing under a very hot water tap to dissolve the remaining sodium carbonate. If necessary, boiling up in HCl afterwards. Hope this is useful information.
When I melt silicate glasses in a Pt crucible, after pouring the melt, and being the crucible still hot I sink it in water at room temperature. It breaks main part of remaining glass and shortens afterwards chemical attack time with HF.
I've recently tried a few methods for cleaning Pt crucibles and found that a 50:50 mix of Lithium metaborate and lithium tetraborate works well to flux metallurgical slags and a succeeding 10 min ultrasonication in 5% - 10% HNO3 seems to efficient to remove the residues.
Those interested at platinum crucibles cleaning may check also: https://www.researchgate.net/post/How_to_clean_up_the_platinum_crucible_used_in_thermal_analysis#5688b6b05cd9e3866c8b4574
Those interested at quartz labware cleaning may check also: https://www.researchgate.net/post/How_do_I_clean_the_quartz_tube_used_for_CVD_synthesis_of_graphene
Stubborn contaminations in platinum crucibles
Besides smelting with potassium pyrophosphate (where the crucibles are filled with it and then are slowly baked to red heat), the following cleaning process is also recommended for stubborn contaminations in platinum crucibles:
Soak the crucible in diluted hydrofluoric acid for at least 24 hours and then boil for 3 hours. After cooling, rinse carefully with water and – if necessary – mechanically clean in an ultrasonic bath. Rinse again and finally boil in distilled water to completely remove the hydrofluoric acid. Prior to reuse, bake at 900°C for one hour. Since hydrofluoric acid corrodes glass, it is recommended to use PTFE containers.
Please keep in mind that both aqua regia and hydrofluoric acid are extremely corrosive and toxic. Hydrofluoric acid is a contact poison which is im mediately resorbed by the skin and is therefore classified as being in the“very toxic” hazard category. Please take safety measures when working with these substances and use safety goggles, protective clothing and gloves.
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