What inquarts with Bismuth Flux?

fireguy

fireguy

Supermoderator
#1
More and more assay laboratories are using flux made with bismuth oxide rather than lead oxide (litharge). There are a variety of reasons to do this. Bismuth is more environmentally friendly, so disposal and recycling are easier. Bismuth is also has less exposure risk. We always recommend wearing proper respirator protection as bismuth flux contains silica, but blood-lead monitoring is not needed and the medical surveillance is less rigorous. This does raise the question of the best type of inquart. Traditionally, inquarts (such as the Herman Inquart) have been a silver lead alloy. It seems counter-intuitive to add lead into the bismuth flux assay. There are two alternatives: 1) You can use a pure silver inquart. However, for the smaller inquart weights (like 2 mg or 4 mg) the inquart is made from very fine wire which can be difficult to handle. 2) You can use a silver copper inquart. These are larger and easier to handle, similar to the silver lead inquarts. But they do not contain lead so will not introduce lead into the bismuth assay. Currently these are available in 2 mg and 4 mg silver weights and further details and pictures can be seen here: http://www.lmine.com/category/copper_silver.html
 
fireguy

fireguy

Supermoderator
#3
Sad Prospector said:
Is the amount of lead in the inquart really significant?
Maybe not. But if you are using bismuth as a way of eliminating lead, it doesn't make sense to add even a small amount of lead to the assay process and potentially contaminate your waste streams with lead.
 
J

JonSnow

New Member
#4
This is an easy fix. I always have a stock solution of silver nitrate which equals 2mg/ml. I make it from reagent grade silver nitrate so there is no question to quality. Of course I always check each new batch of incoming chemicals to be sure. I just mix my assay charge, create a hole in the center of my charge, and add 1ml of my stock AGNO3 using a calibrated pippetor. Then cover with the dry assay charge from the sides of the crucible. I have used this method thousands of times.
There you go. A simple no lead inquart that is accurate every time.

This method works for any type of inquart. Au,Pt,Pd.....
 
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