Transcriber's Note: Underscores "_" before and after a word or phrase indicate _italics_ in the original text. Equal signs "=" before and after a word or phrase indicate =bold= in the original text. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Typographical errors have been silently corrected but other variations in spelling and punctuation remain unaltered. Footnotes are all journal references, so they have been moved to the end of the text. In the original text, the volume number for the journals was double underlined for emphasis. In this book this has been replaced with the use of italics. On the Existence of Active Oxygen. Thesis presented for the attainment of the degree of Doctor of Philosophy at the Johns Hopkins University. by Edward H. Keiser. Baltimore, 1884 On the Existence of Active Oxygen. That a gaseous element can exist in an allotropic condition was first clearly shown by a careful study of the properties of ozone. Although discovered by Schönbein in 1840, chemists were for a long time unable to determine its true nature, and it was not until seven years later that Marignac[1] succeeded in proving that it was oxygen in an allotropic condition. Marignac’s work was confirmed by De la Rive, and subsequently the elaborate researches of Andrews and Tait, and Soret, as well as those of von Bato and Claus have established beyond all question that ozone is an allotropic modification of oxygen, and that its density is one and a half times that of ordinary oxygen. The possibility of the existence of allotropic modifications of oxygen having been thus established it is not surprising that attempts should have been made to find other forms in which this element might occur. As early as 1855 Houzeau[2] stated that when barium superoxide was decomposed with concentrated sulphuric acid, at low temperatures, a colorless gas was evolved which oxidized metals and ammonia. It had a penetrating odor and possessed the power of bleaching litmus paper, and liberated iodine from potassium iodide. By heating the gas to a temperature of 75°C it was completely converted into ordinary oxygen. He calls the gas _nascent_ oxygen and further states that it is probable that whenever oxygen is set free from any of its compounds at low temperatures it is in the nascent or _active_ state.