Sciencemadness Discussion Board

Testing for lead or it's oxides - best method?

temp_RR - 2-4-2019 at 14:12

I want to try an experiment with heating 60/40 lead solder and drawing the fumes through a paper and or cloth filter (vacuum) and then test the filter to see if there is any lead. I also want to try heating lead in a small cast iron pan with a torch and do the same thing. I want to see how much, if any lead comes off an at what temperatures it does or doesn't come off as a vapor. I know the BP of lead is near 3200F but I keep having people telling me it's vaporizing while I solder... They don't seem to understand rosin core solder.

So, does anyone know of a substance, possibly a solution, that I could use to wipe on the filter and reveal Pb or PbO/PbO2/Pb3O4?



Sulaiman - 2-4-2019 at 17:03

Here in EU we do not use lead or rosin in solder for manufacturing
- their negative effects on the environment and health being pretty much accepted.

Where I worked as a repair engineer we used non-rosin cored Pb:Sn or lead-free solder depending upon what we were repairing,
in either case we had extraction/filtering available
https://uk.farnell.com/weller/t0053660699n/fume-extraction-u...
more for the flux fumes than lead,
so you may want to investigate the rosin flux fumes before the lead.

Loptr - 2-4-2019 at 17:07

Rhodizonate or sulfide are most common ions used in kits to react with lead that might be present. You can find lead testing kits online.

SaccharinSlayer751 - 2-4-2019 at 18:09

If you really want to make a lead testing solution at home and are willing to put a bit of work in to do so, there is a quite easy method to do so with sulfides involving nothing but a trip to the hardware store and a propane torch or outdoor stove. I would recommend making a solution of sodium sulfide that you can add to anything that you suspect might contain soluble lead. If it does, a very dark black insoluble precipitate of lead sulfide will form which should be easy to see even in small amounts. I'd be more than happy to post a detailed how to, but only if you are able to get your hands on some elemental sulfur (garden dust), steel wool, and sodium hydroxide (drain cleaner) and are willing and cautious enough to work with H2S. It's pretty serious stuff, 1ppt will kill and you can't smell it after 100ppm, but as long as you are working outside and do everything correctly, there should be minimal risk.

[Edited on 4-3-2019 by SaccharinSlayer751]

temp_RR - 2-4-2019 at 18:20

Quote: Originally posted by Loptr  
Rhodizonate or sulfide are most common ions used in kits to react with lead that might be present. You can find lead testing kits online.


Thanks! That looks perfect for testing lead and it looks like a great prospect for a synth because it's really potassium rhodizonate looks to be relatively expensive buy and should be a fun synth to do.

When you said "or sulfide" what did you mean?

woelen - 2-4-2019 at 23:58

Any soluble sulfide will do the job. Most common is sodium sulfide. You can get that on eBay, but most chemical sellers also sell this chemical, also to private individuals. It is used for hobby purposes, such as toning black and white photographic images.

Be careful with Na2S. It is quite toxic and if you add acid to it you get H2S. H2S is toxic and has an awful smell. It is not as toxic as SaccharinSlayer751 suggests though. At 1 ppt (part per trillion) you won't even smell it. At 1 ppm it has a horrible smell, but otherwise it does no harm, not even when exposure is for several hours. At 10 ppm it irritates the eyes and slowly does damage to them. At 100 ppm it kills your sense of smell in just a few minutes (which receovers, when you are in fresh air again). At exposure to 200 ppm for several minutes it can cause edema and may lead to death. A concentration of 100 ppm is quite high already. That's 100 ml of gas in each cubic meter of air. If you are outside you will have a hard time producing that kind of concentrations.

unionised - 3-4-2019 at 12:26

Quote: Originally posted by woelen  
A At 1 ppt (part per trillion) you won't even smell it.


At 1 ppt (part per thousand), it will kill you.

RedDwarf - 3-4-2019 at 14:41

Which just demonstrates the danger of using TLAs and assuming you mean the same thing as your reader will think :)

SaccharinSlayer751 - 3-4-2019 at 16:00

Quote: Originally posted by RedDwarf  
Which just demonstrates the danger of using TLAs and assuming you mean the same thing as your reader will think :)

My bad, even wikipedia warns that "One part per thousand should generally be spelled out in full and not as 'ppt'"

[Edited on 4-4-2019 by SaccharinSlayer751]

[Edited on 4-4-2019 by SaccharinSlayer751]

SaccharinSlayer751 - 3-4-2019 at 16:00

Quote: Originally posted by RedDwarf  
Which just demonstrates the danger of using TLAs and assuming you mean the same thing as your reader will think :)

My bad, even wikipedia warns that "One part per thousand should generally be spelled out in full and not as 'ppt'"

maldi-tof - 4-4-2019 at 13:59

Hi,

As commented before, lead can be tested via sulfides.
Where I work, we test lead with freshly prepared H2S. It is made warming ferrous sulfide with HCl, and collecting the gas generated (H2S) in water. For the determination, it is better to buffer the solution to pH 4.

It is not a sensitive method for lead. Arsenic, copper, molybdenum, cadmium and silver will turn yellow too.
If you Google: heavy metals 231 USP, you'll read different validated methods to test lead.