Lead Oxide/Litharge (Fake diamond glue)

There really isn't much to this one - Lead (II) Oxide has the forumula Pb (II) O, or PbO.

I started this entry intending to discuss how it was used in generating so-called "lead crystal." All Swarovski, Baccarat, etc., "crystal" is is regular silicon glass with up to about 20% lead oxide added. Lead oxide has a high refractive index (the amount by which the speed of light is retarded in the material compared to a vacuum; that is, a material of refractive index 2 would slow light to half the speed of that of light in a vacuum - refractive index 1).

Why would we want a high-refractive index solid? It's sparkly.

Certain solids reflect light back into themselves via a phenomenon called total internal reflection. This becomes more pronounced in higher-refractive index solids, and appears as "sparkliness." Diamonds are famously high refractive-index, and the cuts used are designed to emphasize total internal reflection. Diamond simulants all must have high indices of refraction to ensure a reasonable facsimile of diamond.

I didn't realize lead oxide was "litharge." One of my favorite books, Surely You're Joking, Mr Feynman!, mentioned it. One chapter was about his trouble getting mail through when he was working on the bomb at Los Alamos (exacerbated by his tendency to deliberately test the censors working there):

So when I went to see my wife in Albuquerque that day, she said, "Well, where's all the stuff?"

I said, "What stuff?"

She said, "Litharge, glycerine, hot dogs, laundry."

I said, "Wait a minute - that was a list?"

She said, "Yes."

"That was a code, I said. "They thought it was a code - litharge, glycerine, etc." (She wanted litharge and glycerine to make a cement to fix an onyx box.)

Apparently, it makes a waterproof cement. Who knew? I like the idea of everyone mixing up their own glue at home.

Have a great weekend.