Sorry, this is not a direct reply to the question, but related to dichromates nonetheless.
I just started working on gum bichromate process and am now preparing chemicals. There's a problem with ammonium dichromate though. Upon dissolving in water (I'm preparing 10% sol'n), small filaments form in the solution. The filaments are dark green/brown in color. They are insoluable and soft in consistency and stick to the walls of the glass beaker. I am using distilled water, but this is the first time i used samples from this particular chemist, so I can not vouch for its purity.
Does anyone have an idea why these filaments appear? And does their appearance mean contamination of the dichromate solution?
I have prepared the solution under dim tungsten light, so exposure to light should not be a problem.
And Mustafa, if I'm able to eliminate this dark green/brown substance I can lend you some solution, so there, I had an answer to your question after all
But if you want to prepare it at home I suggest you get controlled air flow in your working environment or a gas mask from Karaköy. The particular brand of dichromate I purchased had some very fine crystals (normally the crystals are relatively large and easy to work with) which may pose some risks unless there is controlled airflow.