NITROUS OXIDE. Nitrogen monoxide— nitrous oxide — laughing gas — Nr0 — specific gravity 1.52—atomic weight 43.76. A colorous gas possessing a pleasant, slightly sweet smell and taste. Used largely by surgeons and den tists—preferably with a small admixture of oxygen as a general anaesthetic. It is not in flammable and not explosive except in the pres ence of some easily oxidizable material when it.acts in manner similar to oxygen under same conditions. Soluble in water to the extent of approximately one volume at ordinary temper atures and atmospheric pressure. Much more soluble in alcohol and many of the volatile oils. At temperatures below its critical point (30° C —86° F.) it is readily liquefied by pressure. Its critical pressure (tension of the gas at its criti cal temperature) is 75 atmospheres. At tem peratures below the critical the tension of the saturated vapor is approximately as below: —100° C.— Freezes.
— C.-15 lbs. (Atmospheric pressure). C.-30 Atmospheres.
+ 7° C.-50 Atmospheres.
+ 20 —60 Atmospheres.
+ 55 —116 Atmospheres.
The liquefied gas is a colorless and very mobile liquid having a specific gravity of 0.9369, freezes at —100° C. and expands rapidly when heated—is not miscible wsth water but dis solves or mixes readily with alcohol —chloro form—ether and the volatile oils generally. It is also a ready solvent of many gums and hy drocarbons.
If a cylinder containing the liquefied gas be immersed, valve up, in a freezing mixture of ice and salt, in order to condense and freeze any moisture present, and then after attaching a short bent delivery tube to the valve, be in verted with the tube extending into a glass flask and the valve cautiously opened, the first liquid flowing will evaporate with great rapidity and some spluttering until the temperature of the tube and flask are sufficiently reduced, when the liquid will collect in the flask and may be re tained for a considerable period. If the liquid be agitated or the gaseous atmosphere over the liquid be removed by blowing with the mouth or otherwise, the surface will be immediately covered by a thin film of the frozen gas. In this or similar experiments great care is neces sary to prevent the liquid or frozen gas from striking the unprotected skin, as it will quickly freeze the surface and produce an ugly sore similar to that produced by contact with molten lead or other metal.
History.— Nitrous oxide was first prepared by Priestley in 1772 by deoxidizing nitric oxide — NO. In 1823 the gas was liquefied by Far aday by heating anhydrous nitrate of ammonia contained in one limb of a hermetically sealed glass tube bent in the middle at an obtuse angle. The gas together with the water
vapor formed by the decomposition of the salt distilled over into the cooled end of the tube and both being condensed by the pressure and cold to liquids—the gas collected on top of the water.
Through the experiments of Natterer of Vienna and Bianchi of Paris (1845) carbonic acid— nitrous oxide and some other gases were liquefied on a semi-commercial scale by the use of a small but powerful pump specially con structed for the purpose. The pump cylinder of small diameter and long (not unlike a gun barrel) was cooled by a water jacket and deliv ered the gas in successive charges through an automatically operated valve into a strong iron reservoir which was surrounded by ice or a freezing mixture.
Many early observers called attention to the peculiar physiological effects of the gas when breathed: in some instances it would seem prohe able that they must have made use of an impure gas in their experiments. In 1809 Sir Hum phrey Davy mentions among these effects in. toxication and ultimate loss of consciousness and even suggests its use as an anaesthetic. This suggestion bore no fruit until 1844 when Mr. G. 0. Colton in the course of a lecture or entertainment given at Hartford, Conn., ad ministered the gas to a number of individuals from his audience and among others to Mr. Samuel A. Cooley, who in the course of the antics induced by breathing the gas injured his leg quite severely. Upon coming out from un der the influence of the gas Mr. C. stated that he had no recollection of the injury nor did it give him any pain. Dr. Horace Wells, a dentist of Hartford who was present, imme diately suggested the use of the gas as an anaesthetic in the extraction of teeth Within a few days Dr. Wells arranged to put his idea to a test. Mr. Colton adminis tered the gas to Dr. Wells, and Dr. J. M. Riggs, also a Hartford dentist, extracted a tooth from Dr. Wells' mouth. This experiment was a complete success, and monumental, be ing the first recorded instance of a painless surgical operation under the influence of a gen eral anaesthetic. Dr. Wells made use of the gas in a number of minor surgical operations, but, owing to crude methods and imperfect ap paratus, with varying success. Dr. Wells died a little later, and the anaesthetic properties of sul phuric either and chloroform being discovered, the anaesthetic properties of nitrous oxide were apparently forgotten until the year 1862, when its use was revived, this time in New Haven, Conn.