jmdlcar said:
I am STOP saying or writing anything to anyone that write a message.
jmdlcar
I did not mean to offend you & am MOST CERTAINLY sorry if I did :!:
Not sure where to even start here - but will try
You have been a member for about 10 years now - but based on your recent questions you are just beginning your first attempts in silver refining (so it's a learning process)
In one of your threads you asked the question - "how much nitric do I need to dissolve X amount of silver" ?
In reply to that Ralph (palladium) posted the link to the PDF acid work sheet - & there is nothing wrong with that PDF
Ralph is one of our "most respected" members (& a member I VERY MUCH respect) and those numbers posted in that PDF are true - BUT - they are only true "To a Point" --- in other words generally speaking those numbers are true - but they are not absolutely true --- that is because although generally speaking those numbers are true - the amount of actual amount of acid it will take to dissolve a given amount of metal can & WILL change based on the conditions under which the metal is being dissolved --- THAT is true whether you are dissolving gold, silver, copper or other (normally base) metals
In other words - those (PDF) numbers are a general "rule of thumb" but NOT an "absolute law"
Therefore - IF (the big IF) you follow those numbers as a absolute law - you will more often then not - find yourself wasting acid
That is because using those numbers "to the letter of the law" - you will find - that depending on the conditions used in dissolve a given batch of metal - more often then not - one of two things will more likely (then not) happen
1) all your metal will NOT dissolve - so you will need to add more acid - which in turn means you are wasting acid
2) all your metal will dissolve BUT there will still be "free" acid left (so unless you have more metal to add - to use up that free acid) again you are wasting acid
Point # 2 (above) is one of the most common mistakes that new members run into when they dissolve gold with AR --- & then when they use to much nitric in their AR they can't get their gold back (the gold wont drop back out of the AR) so we end up telling them that "their problem" is to much free nitric in the AR so they need to de-NOx the AR to remove the free nitric before their gold will drop
The reason that they end up with free nitric in their AR is because before coming here to the forum - they find info elsewhere on the internet with a "general rule of thumb" for dissolving gold
The general rule of thumb - for dissolving gold - is to use 1 ml 70% nitric with 3 ml HCl to dissolve 1 gram of gold - and that "MAY'" be
close to true if you are trying to dissolve a solid gold coin
However - more often then not - they are dissolving gold foils recovered from a batch fingers - & that changes the condition of dissolving the gold --- in other words - there is a difference between dissolving a one ozt gold coin & dissolving one ozt of gold foils
That difference (which is a condition) is surface area --- an ozt of gold foils has MUCH more surface area then a solid gold coin
Therefore - because the gold foils are VERY thin with LOTS of surface area - the acid does not need to work anywhere near as hard to dissolve the gold - which in turn means it WONT take as much acid to dissolve the gold - compared to dissolving a sold gold coin - which in turn means if you use the "rule of thumb" (1/3 nitric/HCL to dissolve a gram gold) to dissolve gold foils - you ARE going to end up with with free nitric in your AR - which then means you have to de-NOx the AR to get rid of the free nitric - or your gold will not drop - which in turn means you wasted acid in the first place
The same holds true whether you are dissolving gold, silver, copper or some other metal
How much acid it takes to dissolve a given amount of metal WILL change depending on the conditions under which you are dissolving the metal --- in other words - depending on conditions - it may take more acid - or it may take less acid - then the (so called) rule of thumb numbers
the bottom line is that if you follow the rule of thumb numbers - as an absolute law (as in IT TAKES) you will in fact find yourself wasting acid
Therefore - once you understand how conditions effect the amount of acid you need to dissolve a given amount of metal - you can use those conditions to your advantage - so you need to understand the conditions that effect the actual amount of acid it will take to dissolve a batch of metal (& there is NO absolute here - it is "a bit" of a guessing game with each batch)
1) surface area - it takes more acid to dissolve (say) a solid kilo bar of silver then it take if you dissolve (say) that same kilo of silver melted & pour to silver shot --- that's because by pouring the silver to shot you create a whole "lot" more surface area - so the acid does not have to work as hard at dissolving the silver - so you will use less acid
2) dissolving the metal in a closed vessel compared to dissolving the metal in an open vessel - if you dissolve the metal in an open vessel (no cover on the beaker/bucket or pot) it will take more acid then if you put a cover on the vessel - that's because by keeping the NOx in the beaker (or vessel) helps get more use of the acid as "some" of that NOx gets re-absorbed back into the solution during the reaction - instead of letting all the NOx go out the top of the beaker
3) when dissolving silver (or copper) - if you use about half again the (so called) recommended amount of water (distilled) you will get better use of the acid - that's because the NOx stays in the solution better (in stead of just gassing off) thereby you will get more full use of the acid during the reaction
4) Heat makes a difference - to little (or no) heat makes the acid work harder (not the same as - but kind of like surface area effects acid consumption) & on the other hand to much heat will cause NOx to be driven out of the solution during the reaction --- therefore you can start out with your batch on the hot plate to get the reaction started - once it is getting going but not full blown - turn the heat off & the heat of the reaction will do its own thing - then when the reaction is slowing down - turn the heat back on until you are done with the batch --- this will give you better use of your acid
Taking into consideration & using these conditions - I have dissolved successfully (although only a couple times) as much as 500 grams silver with only 350 ml 68% nitric (so .7 ml acid per gram silver - that's 5 tenths of a ml less acid then the "recommended" 1.2 ml acid per gram)
On the average (so sometimes more & sometimes less) - using those conditions to my advantage - I would be willing to say I get away with using only about .9 ml of 68% nitric per gram of silver when doing a batch of silver
To put that in perspective - when I make my electrolyte for my silver cell - I do it in 500 gram (silver) batches - on the "average" I am able to dissolve that 500 grams with "about" 450 ml 68% nitric --- so on a 500 gram batch I am saving "about" 150 ml of nitric --- in other words - according to the rule of thumb - in theory - it should take 600 ml acid to dissolve 500 grams silver - but on average I get away with only "about" 450 ml acid
My point in all of this is that the PDF Ralph posted is actually only a rule of thumb (not an absolute law) - therefore - as a rule of thumb - depending on conditions - it may take more acid - or less acid then the rule to dissolve a given amount of metal --- & IF you use those conditions to your advantage you can almost always (if not always) get away with less acid
Kurt
