xrf testing questions

[rusty marlin]

I have access to an XrF machine and its not showing any arsenic in alloys that by common internet wisdom say there should be some. It is however showing Silicon.
Does anybody know how these machines actually work?
Is it possible its confusing the two elements?
Has arsenic been replaced by silicon as a hardening agent?
Can the machine be programmed to look for specific elements and not report out others?

This is the results I got for sample of plumbers lead (5 pound hexagonal ingot).
lead.........silicon....Ti.........iron......phosp horous
90.00%...4.63%...0.71%..0.94%......0.20%

[JonB_in_Glencoe]

Some years back, I sent some samples to a member with access to a tester, this was before BNE was doing it. Two of my three samples each came back with 3% bismuth, and neither one should have had any bismuth. It was strange that both were 3%. The person that tested them suggested to me, that it's likely an error and maybe the surface was contaminated? I was told to just consider that 3% as likely being 3% more Pb.

The 3rd sample came back as 10-1, which is right near what I predicted it to be.

[rusty marlin]

Found a guide on these machines here:
https://info3.thermofisher.com/LP=92...tal%20analyzer

I'm also going to request a copy of the instruction manual from our Quality peeps to study.

[megasupermagnum]

Is there any chance this lead was drilled or cut with a carbide tooth bit?

[Dusty Bannister]

What would make you expect to find arsenic in plumbers lead? A little antimony, yes. Plumbers lead does not need to be 100% and if the sample has not been properly cleaned, you are going to read whatever trash is deposited during handling.

[Half Dog]

I have taken lead samples to a local university. Their geology department had expensive equipment that could tell me everything in the sample.

[Rickf1985]

I would think that plumbers lead, if it were buried would be likely to show silicone, which is sand. But I also know that BNE has told me that he can program his machine to look for or exclude whatever is above or below programmed parameters. That way you don't end up with a lot of data that is not pertinent to what you are doing. If you look hard enough you will find many elements in your lead but in such small amounts it is senseless to waste time and paper.

[LabGuy]

Speaking as an analytical chemist, XrF is a fast cheep close look. Digesting (in acid) a sample and running by inductively coupled plasma (ICP), and/or ICP mass spectrometry (ICPMS), is significantly more accurate. Every testing method has it’s own inherent errors. But looking at the spectra and the masses makes ICPMS the best, the instruments run about 250K. Unfortunately I retired, and do not have direct access any more. I could call in a few favors, but I’m saving those.

[dale2242]

When I was operating heavy equipment, we would send used oil samples into Caterpillar to get analyzed.
They would always come back saying there was silicon.
Silicon is dirt.

[kevin c]

Are you talking about a hand held analyzer, like a Niton gun of the sort often used by metals recyclers? How the sample is tested and how the analyzer is maintained can change the readings.

BNE describes how he scrapes his samples prior to putting the sensor on the spot to be tested, otherwise the reading includes whatever is on the surface. He probably also cleans the sensor of his lab grade instruments after each use to avoid carry over contamination for the next test, a task I’d guess isn’t a high priority in the scrap yard, where a ball park estimate on the main metals making up the particular type of scrap in question is probably all that’s needed.

I might be under the wrong impression, but, unless the sample or xrf sensor are completely coated in junk, I think the contaminants might only cause low single digit percentage errors.

[Newboy]

When I was operating heavy equipment, we would send used oil samples into Caterpillar to get analyzed.
They would always come back saying there was silicon.
Silicon is dirt.

Oil samples are usually run through an FTIR (Fourier transform infrared spectrometer), which works on a different principle.


Sent from my iPhone using Tapatalk Pro

[JSnover]

When I was operating heavy equipment, we would send used oil samples into Caterpillar to get analyzed.
They would always come back saying there was silicon.
Silicon is dirt.

Turbine engine oil samples also come back with silicon.

[bruce381]

silicon in oils are mostly due to dirt, anti foam additive and even silicon oil contamination

[dtknowles]

Some XRF scans of my alloys.






Some have silicon from who knows where but might be real. The zinc is from wheelweights, the copper is added on purpose.

Tim

[rusty marlin]

I did some reading and some more testing, with a different operator, same XrF unit. I made sure to clean an area of the ingots with a file to insure a fresh surface. Its a portable XrF unit Incoming Receiving uses to confirm material matches the certs.

The same sample of plumbers lead tested before is 100% Pb. None of that extra stuff.

My question on arsenic is based on testing a couple of different batches of WW.
I was finding enough MICRO marked ones I set them aside in 5 gallon pails of their own and melted all the rest together. Hundreds of pounds done in 50-80# batches over a turkey fryer.
There is no arsenic to be found in any of them. I would think it would show up in low percentages as my batch of Monotype D has a low percentage (.035%) Cu and the arsenic is supposed to be on the order of 10x that.
There is no arsenic to be found in the mixed batches or the MICRO batches. Curious, that.

This past Friday I tested some ingots that were made a decade or two ago when I first got into casting. Following Lyman's "Bullet Making Guide"; it says a mixture that compares very favorably to Lyman #2 can be made from the following:
5.5# WW
1# 50/50 bar solder
3.5 pounds of lead.

Well guess what...no it doesn't. It comes out to 95.7Pb 3.4Sn and .85Sb, no wonder I thought it was awfully soft. But having never touched Lyman #2 I had no frame of reference.

So now I have another conundrum. Sunday, I took that same alloy and plugged it into the casting-alloy-mix-master chart and added enough other materials to create a 90/5/5 alloy. Only it came out light. 92.45Pb, 3.93Sn, 3.54Sb and .084 Cu. The copper is coming from the Monotype D. They are flat plates used for working out that were painted with copper paint.

Where did the missing Tin and Antimony go? Everything was weighed to the second decimal from known measured ingots (except the .2# of 95/5). I scaped a second sample area and measured it twice. Slightly different answer, but the same missing Tin and Antimony.

Using the same chart I attempted to make a WW with 2% tin alloy. It came out 1.7% Sn.

I guess I'm ranting, but I'm frustrated. I expect that one follows a recipe and one gets the expected result. And yes, I re-checked the math in the mix chart.

The good news is I checked some lead came for stained glass windows I bought years ago and it turns out it's 55/45 Pb/Sn solder.

[Rickf1985]

If you are using the bullet alloy calculator from Bumpo on here I am pretty sure it tells you somewhere in that program that since it is an Exell program it is not going to give exact results down to the tiniest degree. It is a guide. Excell is a word program, not specific math program. It is not designed to do complex math. If you want to get that exact in your alloy you really should be doing the percentages by hand using real math. And also using KNOW alloys from a foundry like Rotometals. Using things like solder and wheel weights and linotype and expecting to get a known result from an XRF test just ain't gonna happen! You have no idea what is in any of those mentioned alloys other that what is published in old books or what you were told on a forum.

[JonB_in_Glencoe]

Monotype D ... They are flat plates used for working out

used for working out?

How sure are you, that your Monotype D is what Monotype D is defined as?
https://en.wikipedia.org/wiki/Type_metal

[rusty marlin]

used for working out?

How sure are you, that your Monotype D is what Monotype D is defined as?
https://en.wikipedia.org/wiki/Type_metal

Buckets of type set were melted and poured into pie tins for use as weight lifting weights by a very frugal individual, Now I have them.

I am confident that it's Monotype D because it fits the ingredients within 1% of error when measured with the XrF machine and is closer to Monotype D than anything else in the table.

[rusty marlin]

If you are using the bullet alloy calculator from Bumpo on here I am pretty sure it tells you somewhere in that program that since it is an Exell program it is not going to give exact results down to the tiniest degree. It is a guide. Excell is a word program, not specific math program. It is not designed to do complex math. If you want to get that exact in your alloy you really should be doing the percentages by hand using real math. And also using KNOW alloys from a foundry like Rotometals. Using things like solder and wheel weights and linotype and expecting to get a known result from an XRF test just ain't gonna happen! You have no idea what is in any of those mentioned alloys other that what is published in old books or what you were told on a forum.

I have definitely learned my lesson on trusting a printed or internet source, that won't happen again.

I measured the ingots with the XrF machine.
Then used those "known" measured ingots as ingredients in my melt.
I was expecting a known result from known inputs... I am confused as to why 1+1 does not = 2 (or .3+.2+.5 doesn't equal 1) in this case.
I'm not looking for results to the tiniest degree, but within the error of multiple measurements would be nice. +/-0.2%? My melt is off by more than this.
BUT... that does give me an interesting experiment, take multiple readings of the raw materials and look at the high and low readings to get a more broad range of possible outcomes...interesting line of thought.

Our XrF machine goes through a regular inspection protocol and it's a "trusted" piece of measuring equipment.

[kevin c]

Like you, I am confident in my math. But my personal experience and what I’ve been told by folks whose opinion I trust makes me less sure of how much precision is reasonable to expect from xrf analyzers.

I have personally seen a Niton give three different sequential results taken from three different spots on the same clean bar of recovered bullet alloy.

BNE has told me that he generally considers the readings good to +/- 0.1%, but what does that mean for metals that are present only in single digit percentages?

For me, I make up large lots of source alloys, that I mix into large lots of casting alloy, using the same lots in the same proportions. BNE’s analysis tells me that I’m in the ballpark for what I’m shooting for. Since I’m only going at pistol velocities, don’t care about terminal ballistics, and coat all my bullets, I’m good with having a consistent if not precise alloy.

YMMV