戴維發現麻醉劑時總共失敗了多少次？

近代最早发明全身麻醉剂的人是19世纪初期的英国化学家戴维。有一天，他牙疼得厉害，当他走进一间充有“一氧化二氮”气体房间时，牙齿忽然不感觉疼了。好奇心使戴维做了很多次试验，从而证明了一氧化二氮具有麻醉作用。因为戴闻到这种气体时感到很爽快，于是称它为“笑气”。
大英百科全書則說:
In his (Davy, Sir Humphry) small laboratory, he prepared and inhaled nitrous oxide (laughing gas) in order to test a claim that it was the "principle of contagion", that is caused diseases. On Gilbert's recommendation, he was appointed (1798) chemical superintendent of the Pnueumatic Institution, founded at Clifton to inquire into the possible therapeutic uses of various gases. Davy attacked the problem with characteristic enthusiam, evincing an outstanding talent for experimental inquiry. He investigated the composition of the oxides and acids of nitrogen, as well as ammonia and persuaded his scientific and literary friends, to report the effect of inhaling nitrous oxides. He nearly lost his own life inhaling water gas, a mixture of hydrogen and carbon monoxide sometimes used as fuel. The account of this work, published as Researches, Chemical and Philosophical (1800), immediately established his reputation...