Sciencemadness Discussion Board

Test for Lead in Alcohol

binbin - 3-7-2015 at 22:25

What would be the best way to perform a test for lead in ethanol with great accuracy?

Thanks,

Zephyr - 3-7-2015 at 22:52

To properly answer your question we need some more information.
How accurately?
Quantitatively?
How much are you willing to spend?
which concentrations will it be in?

I recently made some potassium rhodizonate which can be used qualitatively to test for lead...

If its as a salt in large concentrations then you could try and precipitate it and weigh it I guess.

binbin - 3-7-2015 at 23:05

Well, as accurately as possible within $50 or so. In the end, i'd just like to see if lead is being leached from brass fittings. So a simple, yes lead, or no lead test would be great. But it would also be good to perform a titration to see exactly how much lead is in an alcohol solution.

The "great accuracy" was meant more of a, "it would be cool if.." but in the end, I'd just like to see if there is lead, or not.



[Edited on 4-7-2015 by binbin]

aga - 4-7-2015 at 04:20

http://www.docbrown.info/page13/ChemicalTests/ChemicalTestsc...

http://community.boredofstudies.org/241/chemical-monitoring-...

"generally you add Hydrochloric acid to a solution of cations. If a white precipitate forms (this is lead chloride), then lead ions are present. Judging by your question, i think you mean an additional test. To verify the lead ions, you cann add pottassium iodide and the lead ions will react with the iodide ion forming lead iodide which is a yellow precipitate "

The reaction with HCl seems to take quite a while, and at least one other reference suggests leaving it overnight to react.

kecskesajt - 4-7-2015 at 05:25

Well,lead chloride has a solubility of 10.8g/L.So if 5g of lead chloride formed,it cannot be detected but it is poisonus.

Boffis - 4-7-2015 at 05:55

Pinkhippo's suggestion that you use potassium or sodium rhodizonate is probably the best test for lead. If you evaporate down say 10ml on a white porcelain bowl you should be able to detect less than 0.1 microgram of lead. Lead gives a brownish purple precipitate and barium a reddish brown precipitate. Several other metals also give precipitates but treatment of the precipitate with very dilute (0.01M) HCl decolourises the other precipitates but turns the lead ppt to a beautiful intense violet and that of barium a crimson colour. I use this test test to not only detect Pb and Ba but to estimate the ratio of the of these metals present in minerals.

Other reagents include gallocyanine which can also be prepared easily if you have access to dimethylaniline.

@ Pinkhippo do you think it would be worth starting a thread dedicated just to the preparation and use of this type of microchemical reagent?

blogfast25 - 4-7-2015 at 06:11

Much simpler and more widely used than rhodizonate is simply PbS (black and very insoluble). Also PbCrO4 (yellow and very insoluble).

If you're going to concentrate the lead by evaporating off the alcohol, these tests are good enough.

On lead detection as PbS, there's a very good Utoob somewhere.

K Rhodizonate by Nurdrage:

https://www.youtube.com/watch?v=BLmycZ2nrt0


[Edited on 4-7-2015 by blogfast25]

AJKOER - 4-7-2015 at 07:23

Here is a published work out of Nigeria testing local wine/fermented berry drinks. Link: [Edit corrected] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256578/

The wines are subject to HNO3/H2O2 pre testing to determine levels of heavy metals.

I think this work can be of use not only for the procedures employed, but also provides some data on a particular locale heavy metal levels for comparison to your sample.

Also, there is possible a statistical regression relationship between soil levels of heavy metals and your drink contents, or at least, a good testable proposition.

[Edited on 5-7-2015 by AJKOER]

kecskesajt - 4-7-2015 at 08:04

Quote: Originally posted by AJKOER  
Here is a published work out of Nigeria testing local wine/fermented berry drinks. Link: http://www.sciencemadness.org/talk/viewthread.php?tid=62922

The wines are subject to HNO3/H2O2 pre testing to determine levels of heavy metals.

I think this work can be of use not only for the procedures employed, but also provides some data on a particular locale heavy metal levels for comparison to your sample.

Also, there is possible a statistical regression relationship between soil levels of heavy metals and your drink contents, or at least, a good testable proposition.



[Edited on 4-7-2015 by AJKOER]

Wrong link.

Boffis - 4-7-2015 at 08:27

@Blogfast H2S is is very sensitive test but it is not very specific since about a quarter of the metals in the periodic table form insoluble sulphides. The chromate test is more specific but less sensitive and calcium also forms a yellow ppt and there could be a lot more calcium around than lead. To prevent interference for calcium (and Sr, Ba etc ) careful buffering is required.

Hydrogen sulphide is merely a collection reagent for groups of metals.

binbin - 4-7-2015 at 08:33

I checked out Nurdrage's video. However he mentioned at the end of the lead check video that in some instances, even products he knew contained lead did not turn color upon contact. To be 100% sure, then use a professional kit or lab.

What about something like this? http://www.firstalert.com/battery/65-environmental/1033-diy-...

blogfast25 - 4-7-2015 at 10:29

Quote: Originally posted by Boffis  
@Blogfast H2S is is very sensitive test but it is not very specific since about a quarter of the metals in the periodic table form insoluble sulphides. The chromate test is more specific but less sensitive and calcium also forms a yellow ppt and there could be a lot more calcium around than lead. To prevent interference for calcium (and Sr, Ba etc ) careful buffering is required.

Hydrogen sulphide is merely a collection reagent for groups of metals.


Since as we're looking at brass, you'd only need to buffer against zinc, leaving on possible confusion between Cu and Pb. Which is where a chromate test could come in handy.

Rhodizonate isn't perfect either.

Anodic Stripping Voltammetry for Trace Lead Detection

WGTR - 4-7-2015 at 11:31

A more complicated solution, but if the application is important, then there are labs that run these types of tests.

Attachment: PDF-23-Experiment5.pdf (180kB)
This file has been downloaded 527 times

blogfast25 - 4-7-2015 at 13:35

Quote: Originally posted by WGTR  
A more complicated solution, but if the application is important, then there are labs that run these types of tests.



That method is for watery solutions. The alcohol would at least have to be diluted somewhat.

Reminds me of polarography: halcyon days.

[Edited on 4-7-2015 by blogfast25]

aga - 4-7-2015 at 13:39

Would i be a total Fool by asking if Pb always renders ions in water, or could there be undissolved Pb in the water ?

Sulaiman - 4-7-2015 at 13:52

shine a laser pen through the liquid
any suspended matter will be visible
Tyndall effect https://en.wikipedia.org/wiki/Tyndall_effect
e.g. https://www.youtube.com/watch?v=vIUiK-ef8Hs

[Edited on 4-7-2015 by Sulaiman]

aga - 4-7-2015 at 14:07

Lead is said to be quite Heavy as i recall ...

Sulaiman - 4-7-2015 at 14:34

give it a stir/shake before testing !

aga - 4-7-2015 at 15:07

So, if it's to get water tasting better, involving shake/stir then vacuum filtering ...

"Just do the shake-n-vac to get the freshness back ..."

Anyway, how would one do a test for particulate elemental Pb in water ?

HCl again ?

blogfast25 - 4-7-2015 at 15:32

Quote: Originally posted by aga  
Lead is said to be quite Heavy as i recall ...


It will simply sink, forming sediment. Lead in water is Pb<sup>2+</sup>

Zephyr - 4-7-2015 at 16:37

Quote: Originally posted by Boffis  

@ Pinkhippo do you think it would be worth starting a thread dedicated just to the preparation and use of this type of microchemical reagent?


Yes that would be great if others want to experiment with similar tests, I know I would. It would be nice to collect a large array of similar tests so in the event of a false positive/negative it could be crosschecked to establish greater accuracy.

I prepared mine with great success using Nurdrage's method.

binbin - 4-7-2015 at 18:04

On the distilling forums, there is a tale going around that if the brass fitting containing lead is in the lower part of the column, the lead will not be carried up by the alcohol vapours to the condenser. However if the brass/lead issue is after the head of the column, the lead will continue on to the distillate.

Any truth in this?

macckone - 4-7-2015 at 20:05

Quote: Originally posted by binbin  
On the distilling forums, there is a tale going around that if the brass fitting containing lead is in the lower part of the column, the lead will not be carried up by the alcohol vapours to the condenser. However if the brass/lead issue is after the head of the column, the lead will continue on to the distillate.

Any truth in this?


Lead is non-volatile so it won't distill but you could get small amounts of carry-over however if it is dissolved in the solution on the condenser side it will flow down. However the amount of lead in brass is usually small and the amount dissolved is even smaller. Newer brass for drinking water systems is lead free in the US.

subsecret - 4-7-2015 at 20:40

Depending on how much you drink, you might still sustain damage even if you can't see a rhodizonate/sulfide/chromate precipitate. Soluble lead doesn't leave the body easily, and small amounts can build up over time. You'd need something better than precipitation to analyse those small amounts of lead. Lead-free brass is the way to go.

binbin - 5-7-2015 at 12:15

Quote: Originally posted by subsecret  
Depending on how much you drink, you might still sustain damage even if you can't see a rhodizonate/sulfide/chromate precipitate. Soluble lead doesn't leave the body easily, and small amounts can build up over time. You'd need something better than precipitation to analyse those small amounts of lead. Lead-free brass is the way to go.


Or no brass at all. Raw copper can be found still, it'll be more expensive and harder to find for some parts, but can be found. To be considered lead free, brass only needs to contain less than 0.25% lead, which is still not 0%.

aga - 5-7-2015 at 13:58

If this is for a Hooch Rig, why not just add Pb chelating agents such as Edetate Calcium Disodium (CaNa2EDTA) to your Thumper and steal the march on your competition ?

"96% Hooch with no Lead you'll ever know about !"



Molecular Manipulations - 5-7-2015 at 21:09

Why not just copper or nickel plate your brass? Very simple to do and cheap.

AJKOER - 6-7-2015 at 05:47

Some toxicity statistics from the CDC on select Lead salts (link: http://www.cdc.gov/niosh/idlh/7439921.html ):

"ACUTE TOXICITY DATA:
Lethal dose data:
Species Reference Route LD50 (mg/kg) LDLo (mg/kg) Adjusted LD Derived value
PbO Dog Flury and Zernik 1935 oral ----- 1,400 9,114 mg Pb/m3 911 mg Pb/m3
PbC4H6O4 Dog Flury and Zernik 1935 oral ----- 300 1,344 mg Pb/m3 134 mg Pb/m3
PbCl2 G. pig Budavair 1989 oral ----- 1,500 7,770 mg Pb/m3. 770 mg Pb/m3
Pb(NO3)2 G.pig Tartler 1941 oral ----- 500 2,205 mg Pb/m3. 221 mg Pb/m3
Pb(CN)2 Rat NRC 1953 i.p. ----- 100 560 mg Pb/m3 56 mg Pb/m3

Human data: It has been reported that 714 mg/kg of lead acetate (i.e., about 450 mg/kg of lead) is the lethal oral dose [Takahashi 1975]. [Note: An oral dose of 450 mg Pb/kg is equivalent to a 70-kg worker being exposed to 21,000 mg Pb/m3 for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]
Revised IDLH: 100 mg Pb/m3

Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for lead compounds. The revised IDLH for lead compounds is 100 mg Pb/m3 based on acute oral toxicity data in humans [Takahashi 1975] and animals [Flury and Zernik 1935]. [Note: OSHA currently requires in 29 CFR 1919.1025 that workers be provided with and required to wear and use the "most protective" respirators in concentrations exceeding 100 mg Pb/m3 (i.e., 2,000 ´ the current OSHA PEL of 0.05 mg Pb/m3).]"

My take on the above is that the toxicity of Pb varies greatly depending on the Lead salt in question. The more soluble in general the greater the risk. Here is a solubility reference of Lead salts in water, HCl,... https://books.google.com/books?id=d1JMAAAAMAAJ&pg=PA357&...

Unfortunately, in our case here, the actetate form of Lead, formed in fermented wines and such, is more problematic.

My point here is knowing the elemental amount of Pb present should be combined with information on the likely Lead salt ingested as well.

blogfast25 - 6-7-2015 at 07:35

Quote: Originally posted by AJKOER  
Some toxicity statistics from the CDC on select Lead salts (link: http://www.cdc.gov/niosh/idlh/7439921.html ):

"ACUTE TOXICITY DATA:
Lethal dose data:
Species Reference Route LD50 (mg/kg) LDLo (mg/kg) Adjusted LD Derived value
PbO Dog Flury and Zernik 1935 oral ----- 1,400 9,114 mg Pb/m3 911 mg Pb/m3
PbC4H6O4 Dog Flury and Zernik 1935 oral ----- 300 1,344 mg Pb/m3 134 mg Pb/m3
PbCl2 G. pig Budavair 1989 oral ----- 1,500 7,770 mg Pb/m3. 770 mg Pb/m3
Pb(NO3)2 G.pig Tartler 1941 oral ----- 500 2,205 mg Pb/m3. 221 mg Pb/m3
Pb(CN)2 Rat NRC 1953 i.p. ----- 100 560 mg Pb/m3 56 mg Pb/m3

Human data: It has been reported that 714 mg/kg of lead acetate (i.e., about 450 mg/kg of lead) is the lethal oral dose [Takahashi 1975]. [Note: An oral dose of 450 mg Pb/kg is equivalent to a 70-kg worker being exposed to 21,000 mg Pb/m3 for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]
Revised IDLH: 100 mg Pb/m3

Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for lead compounds. The revised IDLH for lead compounds is 100 mg Pb/m3 based on acute oral toxicity data in humans [Takahashi 1975] and animals [Flury and Zernik 1935]. [Note: OSHA currently requires in 29 CFR 1919.1025 that workers be provided with and required to wear and use the "most protective" respirators in concentrations exceeding 100 mg Pb/m3 (i.e., 2,000 ´ the current OSHA PEL of 0.05 mg Pb/m3).]"

My take on the above is that the toxicity of Pb varies greatly depending on the Lead salt in question. The more soluble in general the greater the risk. Here is a solubility reference of Lead salts in water, HCl,... https://books.google.com/books?id=d1JMAAAAMAAJ&pg=PA357&...

Unfortunately, in our case here, the actetate form of Lead, formed in fermented wines and such, is more problematic.

My point here is knowing the elemental amount of Pb present should be combined with information on the likely Lead salt ingested as well.


On your last point, it's unlikely the accompanying anion affects the toxicity of Pb<sup>2+</sup>(aq) much, if at all.

Far more important than the LD50 is the cumulative nature of lead in the human body. Long time, low level exposure to lead eventually causes toxicity. See e.g. the alarming lead levels in children's teeth, during the use of tetraethyl lead as an anti-knocking agent.