Pure phosphuretted hydrogen is distinguished by the following properties: 1. It explodes when coming into the atmosphere in bubbles, and a white ring of smoke subsequently ascends: 2. It is unfit for respiration, and for supporting combustion: 3. Its specific gravity is 1.1 nearly, that of atmospheric air being unity: 4. Water absorbs fully ⅛ of its bulk of this gas, which is expelled again by ebullition or by agitation with other gases, but not without some loss: 5. A small portion being electrified for some time, deposits abundance of phosphorus, and expands from one volume to 1⅓ nearly, which is found to be pure hydrogen: 6. Liquid oxymuriate of lime absorbs phosphuretted hydrogen, converting it into phosphoric acid and water, and leaves any free hydrogen that may be present; hence we are enabled to ascertain the proportion of free hydrogen in any such mixture, an important point as far as regards this gas: 7. One volume of pure phosphuretted hydrogen, requires two volumes of oxygen for its complete combustion by an electric spark, in Volta’s eudiometer; (the gases must be previously mixed in a tube not more than ³/₁₀ of an inch in diameter, to prevent an explosion in the act of mixing, after which they may safely be transferred into any other vessel); the result of the combustion is phosphoric acid and water: 8. One volume of phosphuretted hydrogen, mixed with from 2 to 6 volumes of nitrous gas, may be exploded by electricity in Volta’s eudiometer; or it may be exploded by sending up a bubble of oxygen, without electricity; in like manner, may the mixtures of phosphuretted hydrogen and oxygen be exploded by a bubble of nitrous gas: 9. One volume of phosphuretted hydrogen, mixed with 4, less or more, of nitrous oxide, is also explosive by electricity, but the mixture undergoes no change without electricity, at least in a day: 10. Mixtures of phosphuretted hydrogen and nitrous gas have a slow chemical action, by which in from 1 to 12 hours, the phosphuretted hydrogen is burnt and the nitrous gas decomposed into nitrous oxide and azotic gas: 11. According to Sir H. Davy and Dr. Thomson, phosphuretted hydrogen gas being heated along with sulphur in a dry tube, the gas is decomposed and a new gas, sulphuretted hydrogen, is formed, and the phosphorus unites with the sulphur. Davy says the gas is doubled in volume by this operation; but Thomson says it remains the same; some doubt therefore exists respecting this fact: 12. When phosphuretted hydrogen gas is let up to oxymuriatic acid gas, a quick combustion with a yellow flame is observed, and the result varies according to the proportions: when one volume phosphuretted hydrogen is put to 3 or 4 of acid gas, both of the gases disappear, and muriatic and phosphoric acids are produced.