Aqua regia is unstable. Try EtOH/KOH bath to clean from organics

Aqua regia & chromic acid are both very strong oxidizing agents with each having positive & negative aspects. During my postgraduate studies we used to follow a lengthy protocol to clean glassware until the glass becomes "ultra" clean. Our way was similar to what you find in this reference  from the Department of Chemistry at UNIVERSITY of DELAWARE. My regards.

http://www.udel.edu/chem/GlassShop/GlasswareCare.htm

Just to comment as scientist and in electron microscopy:

my practical experience is that in former days I used self made chromo-sulfuric acid for serious cleaning of glassware (also regularly and periodically  - at least one time/ year the glass flasks for taking up the freshly made A. bidest. from the still).

Since this solution hardly should be purchased/handled - working with (since it is designated hazardous chemical solution and has been marked as ) I don't do it any more. Aqua regia for Lab-glassware seems a bit overkill I guess, but it might depend on the task you have to do to get "super-clean/ultraclean glassware.

So our responses might also depend on what you are willing to share about your .

Regards, Wolfgang

@ Yurii (and, naturally, Fawad):  

naturally seems good and effective, but  IMHO is also really a bit risky / dangerous stuff (also to handle with).

"Lab-glass-ware" usually reacts (at least when used often) with ultra-alkaline solutions in bad manner in altering the glass surface (hence atomic-molecular structure of the silicate). Naturally it (use of such highly basic solutions)  may depend also on the type of glass to be cleaned. 

In my profession commercially available glass cleaning solution (e.g. Fast Alkaline Cleaning Agents like Mucasol or others) are sufficient if they are applied properly: right mixing ratio, right duration, eventually manually brushing and, last but not least: sufficient washing with clear(hot) water as well as A. dest.(A. bidest). If you don't trust such a cleaning procedure, you also can add (after soaking in alkaline solution) after a first washing application 5-10% H2O2-solution for 30-45 minutes. 

I found an interesting and informative technical bulletin created by SIGMA-ALDRICH on Lab-Glassware cleaning

[quote: (end of quote)]

@ https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Aldrich/Bulletin/al_techbull_al228.pdf

and ("scientifically biased") @ http://www.ehs.wisc.edu/chem/GlasswareCleaning.pdf

which both might be useful (besides many other info found in the web).

Disclaimer:  not affiliated with any Company mentioned in my reply, no financial interest.

Best wishes and regards, Wolfgang

chromic acid

Dear Wolfgang,

I agree with your comments. Just couple words. EtOH/KOH (or i-PrOH/KOH) is much less dangerous  compared with others. A borosilicate glass is pretty stable in EtOH/KOH, but it's not recommended to use it for highly basic solutions. 

Dear Yuri,

I did not want to criticize your proposal...  as always...it depends: As long as you don't mix KOH as "saturated" *) into EtOH or i-PrOH this your proposal might work (and it might also depend on the allowed effective  time of the cleaning process. So it might be helpful for all others if you add a ratio for mixing KOH with the alcohol(s). 

*)I have worked with such saturated NaOH or KOH/EtOH-mixtures on epoxide (resin) sections on microscopic glass slides knowing about the "reaction" with "normal" lab-glass flasks (ok, the forming solution was stored up to 5 months)....

Important will be also the final washing of the glassware afterwards....and which purpose the glassware will serve again. Therefore:

As long as Fawad Ahmad will not tell about the cleaning task proper we can only guess about the "best "option....

Thank you nevertheless for your acknowledged comment, best wishes and regards, Wolfgang

Thank you so much sir Wolfgang H. Muss .........sir i am working on synthesis of Ru-Nanoparticles ..........and i am using three neck flasks( at 250 degree centigrade) but i can not reproduce my results so that is why i am worried about the cleaning 

Dear Fawad, thanks a lot….now we / one can imagine the task for the grade of “cleanness” and search for more special solution.

Not knowing if you have the opportunity to search in e.g. < google > for reports or recommendations in cleaning glassware or even if you eventually could or have tried such a search I have done such a search by the keywords you can find (with some results) for your convenience in the attached pdf.

I understand that it might be troublesome to get alll these informations in short time and I don’t know whether the hints, tipps or “scientifically reported on cleaning glass ware” might be helpful for solving your problem….anyway here you go….best of luck and keep “trying”! Regards, Wolfgang

Last but not least: it seems .

But I have learned from the search that there are used several cleaning techniques for glassware depending on the task of analysis to be performed.

You need not addressing me , since I am an informal person, as my first name is really sufficient (:-)) (J)

i am really thankful to you sir Wolfgang H. Muss for your kind cooperation, you mentioned that i am an informal person but for me all informal persons are very respectable. 

Dear resepcted Mr. Fawad Ahmad, M.Phil in Physical Chemistry an PhD student,

you’re welcome.

Best wishes and good luck.

Wolfgang

We are using  i-PrOH/KOH a cleaning agent for glass wears, it is much safer compared with others.