How To: Detect poisonous arsenic levels using the toxicological Marsh test

Was Napoleon's death really due to stomach cancer, or was it arsenic poisoning? Some scientist believe the latter. Arsenic poisoning was a deadly weapon in that era, because it was undetectable when administered over a long period of time, making murder seem like natural causes. But if arsenic (As) is poisonous to most multicellular life, then what's with the newest NASA discovery?

All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Yet, NASA recently found a new life form (a bacteria) on Earth, in Mono Lake, California, that lives on arsenic instead of phosphorus. Call it an arsenic bacteria. This is a huge discovery that could change the way we think about life – both extraterrestrial and terrestrial. But how is this possible? Who knows. It's up to NASA to explain that one.

In light of NASA newest discovery, we thought we show you a video about arsenic— how to detect arsenic using the Marsh test. If you're a chemist or into forensic toxicology, you'll love this how-to. The Marsh test allows you to easily detect arsenic, along with antimony and germanium, and was use more commonly in the olden days when arsenic poisoning was popular.

First, add some zinc to the test tube. Then, the arsenic compound, and in this case, it's arsenious acid = As(OH)3. Then, place a stopper with a dripping funnel filled with hydrochloric acid onto the test tube. The reaction of zinc with the hydrochloric acid sets produces nascent hydrogen, which reacts with the arsenic compound to form arsine. The arsine bubbles through the hydrogen to the glass pipette. This arsine/hydrogen mixture is very flammable. Ignite it at the end of the pipette, which causes pure arsenic to be condensed out of the flame.

The lowest level of detection for this test is 1µg.

Click here for instructions in German.