I was at a client who had a request from a customer to provide sample of powdered silver chloride. The end user was using it as a component in a glaze he makes up for coloring glass. The glaze is painted on to the glass and fired.
My first thought was easy, dissolve some fine silver in nitric and water, drop out the silver as a chloride with hydrochloric, filter, rinse and dry at 225ºF. Well, after drying we tried to break up the clumps to make powder in a mortar and pestle. The chlorides didn't just crumble, they clumped together into flat flakes and assumed the shape of the pestle. I assumed it still was a little moist and went to plan B.
I put the silver chloride in a scorifier and put it in a furnace at 900ºF to melt the chlorides. They melted into a nice liquid looking like maple syrup but thinner. I poured that into a shallow stainless tray where it immediately hardened and peeled off quite easily. Now I figured it would crush up nicely. Well not so fast, the solidified silver chloride bent into the shape of the mortar and did not break up. It behaved like a plastic and had no intention of cracking into smaller pieces.
I never worked with silver chlorides in this way, usually my molten chlorides were large chunks and were reduced in a large tumbler back to metal but now I needed it as a chloride powder.
The customer told us his client used the silver chloride as a component in a glaze and sent me a picture of the silver chloride he was using. It was slightly gray in color and powdery with a few small clumps maybe 5 mm in size. I knew there was a bucket of rinsed silver chlorides from aqua regia digestions being saved to collect until it was worth processing so I took out a few ounces, rinsed it well, and dried it at 225ºF for an hour and it crushed up into powder easily.
I assume the silver chloride I made from silver nitrate was too pure and exhibited the plasticity I described but the silver chloride from a refining operation, which had gold and base metals in the original alloy, apparently was "contaminated" enough that it did not exhibit the physical properties that prevented the crushing into powder of the finer silver. Weird. I do want to run an AA on a sample of the powder made this way just to check the purity but as these glazes do utilize other base metals, anything over 98% should be fine. (As long as that 2% isn't gold!)
Has anyone else seen this behavior with silver chloride?
My first thought was easy, dissolve some fine silver in nitric and water, drop out the silver as a chloride with hydrochloric, filter, rinse and dry at 225ºF. Well, after drying we tried to break up the clumps to make powder in a mortar and pestle. The chlorides didn't just crumble, they clumped together into flat flakes and assumed the shape of the pestle. I assumed it still was a little moist and went to plan B.
I put the silver chloride in a scorifier and put it in a furnace at 900ºF to melt the chlorides. They melted into a nice liquid looking like maple syrup but thinner. I poured that into a shallow stainless tray where it immediately hardened and peeled off quite easily. Now I figured it would crush up nicely. Well not so fast, the solidified silver chloride bent into the shape of the mortar and did not break up. It behaved like a plastic and had no intention of cracking into smaller pieces.
I never worked with silver chlorides in this way, usually my molten chlorides were large chunks and were reduced in a large tumbler back to metal but now I needed it as a chloride powder.
The customer told us his client used the silver chloride as a component in a glaze and sent me a picture of the silver chloride he was using. It was slightly gray in color and powdery with a few small clumps maybe 5 mm in size. I knew there was a bucket of rinsed silver chlorides from aqua regia digestions being saved to collect until it was worth processing so I took out a few ounces, rinsed it well, and dried it at 225ºF for an hour and it crushed up into powder easily.
I assume the silver chloride I made from silver nitrate was too pure and exhibited the plasticity I described but the silver chloride from a refining operation, which had gold and base metals in the original alloy, apparently was "contaminated" enough that it did not exhibit the physical properties that prevented the crushing into powder of the finer silver. Weird. I do want to run an AA on a sample of the powder made this way just to check the purity but as these glazes do utilize other base metals, anything over 98% should be fine. (As long as that 2% isn't gold!)
Has anyone else seen this behavior with silver chloride?