CompuServe Messages

Doug, The "garlic" smell is arsine gas, AsH3. You can also get stibine SbH3 from antimony containing minerals, and phosphine PH3 from a -few- phosphorous containing minerals laid down in hydrothermal reduction zones. They all smell garlicy. In a lab, if you sniff one after another, you can learn to tell them apart. These days, what with the Safety Nazis, such an experimental procedure would be Ganz Verboten, because all three are really nasty poisons. Personally, I think it would be darn near impossible to volatilize enough from a hunk of rock at room temperature to cause trouble. All of these gasses are detectable at very low concentrations and they all smell BAD. The biggest failure of the "sniff" test is that it fails if the arsenic species is fully oxidized, or complexed with sulfur. A more sensitive test might be to volatilize the arsenic in the reducing zone of a blowpipe and note the garlic odor of the resulting gases. There are a whole lot of wet tests for arsenic, but offhand I can't think of any that would be suitable for someone in the field. — Norm