autumnwillow said:
Sorry for posting on a very old topic. I suddenly got interested in silver assaying to compare the silver chloride method of refining vs the electrolytic refining and I'm also interested in buying silver as I have rejected most of the offers I had before. If the assays would return a very small fraction then I guess an electrolytic refining is not worth the time.
I am not a chemist but if anyone is willing to teach for a dummy like me I would really appreciate it.
I have a burette, flasks, fume hood, acids and .001g scale.
From what I understand silver is assayed thru the following steps:
1) Weigh the sample, preferably 1g.
2) Dissolve in 50/50 nitric.
3) Titrate w/ what? 32 percent HCL? 50 percent NaOH? What are the ratios? What ml to what gram of pure silver?
4) What are the indicators?
If there is a book you could recommend I would love to read it. I tried google with no luck understanding what they are talking about. Heh
Keita.
I once ran about 8,000 titrations, of maybe 100 total different metals or types, in a 9 month period. I also once ran about 6000 silver assays in a 4 year period, using the Volhard method, which I assume you want to use. And a lot more in between. I'm just saying I've done a lot of titrations.
Your final accuracy is never better than the least accurate piece of equipment you're using. In this case, this is the scale and the buret. Inexperience, especially in recognizing the end-point, and improper technique (like not reading the buret level or using the meniscus wrong) can severely affect the accuracy.
Your accuracy with a .001g scale. If your scale reads 1 .000g, it is actually saying it's somewhere between .995g and 1.005 (1.004999... really). This is not accurate enough to distinguish between .999 and .9999. At best, you would only know for sure that it was at least 99.5 percent pure.With a .0001g scale, the best you could guarantee would be 99.95 percent pure. However, when titrating, the buret accuracy would very likely be less than that of the ,0001g scale.
What I'm saying is that it's not that easy to determine whether or not it is 99.99 percent pure. If you properly operate your cell, you could very possibly produce 4 nines silver. Probably the most important thing is rinse the crystal very, very well. Spongy, fluffy crystal won't rinse well. Strive for a short stubby hard crystal. Keep the silver content of the cell at least 60g/l and the copper below about 80 g/l. Operate in a fairly clean room not close to a gas melting furnace or incinerator. Don't reuse muslin filters.