yellow precipitate

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arthur kierski

Well-known member
Joined
Feb 10, 2008
Messages
1,090
Location
são paulo---brazil
when evaporating a rhodium sulphate solution for measuring its volume,sometimes a yellow precipitate is formed--- I always thought that it was lead sulphate---but a friend in the forum,comented that lead sulphate is a white powder--i made a quick research and found that lead oxide is a yellow powder----when my rh sulphate solution forms this yellow powder,the quality of the plating sollution is bad---my question is :could a sulphate solution contaminated with lead be purified by evaporating the solution and then precipitating the yellow powder(pbo?) out? i know ,as an example,that lead cchloride is eliminated by hot water -----thanks for any coments---regards to all--------------------------------------------------------------------------------------------------------------------------------------------------------------Arthur Kierski
 
Lino,so what do you think this yellow precipitate is?there are few inorganic yellow precipitates--Anyway,every time that this precipitate is formed,the quality of the plating pieces are bad----when i eliminate this yellow precipitate with filtation,the quality of the pieces are esplendid(very brilliant)---- i do not know what this precipitate is--but for years,i precipitate out from solutions,and the quality of my plating solutions are very good----maybe the chemistry theory,is diferrent from the practical----but a yellow precipitated is formed(sometimes),and althoughi did not know that pbso4 decomposes at 1200C,i had the courage to expose this problem to the forum-----up to know this yellow precipitate remains (for me) nasty lead oxide(pbo)-----thanks all----if i was sure of everything,i would not need help from this magnificent forum
 
Please clear up: The crystals dissolve in water? sulfuric acid? are they matte or bright (including hydration water)?
 
the crystals,do not dissolve in water--instead of dissolving they appear when the solutionn is heated(this solution have 50ml of free acid sulpuric)--and the collor of this precipitate is a yellow pasty mud(like a mustard)--not a crystal type of precipitate
 
The objects to be plated are,copper ,gold plated rings,silver plated necklaces-----but the rh plating solutions is new(without the yellow precipitates)--if ,not pure,these objects plated, have a horrible aspect-------the anodes are usually platinum-----thanks for the interest---- Arthur
 
the objects are cleaned before plating--the bath is diluted rh sulphate solution(made by me)--yes a current is passed during plating--- To make clearer:the rh plating solution is manufactured by me---and the yellow precipitate is eliminated,before i sell the solution to my customers----cannot say more,because of comercial secrets
 
I meant to switch on current before you put objects in. From what you said carbonates of silver or copper may be the cause
 
the only filtration that my clients or i do,is sometimes with activated carbon---this is done only whem the pieces plated lose their brightness---Lino,the question asked,was what is the yellow salt that forms sometimes ,whem evaporating a rh plating solution---i told you that precipitating out ,this yellow salt,the plating solution becames a very good plating solution---it is not affecting my work--i just was curious ,because a member said that Pbso4 is a white powder(and is really a white powder)--thanks for all your coments--and my regardas to you---------Arthur Kierski
 
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