COMMON NAMES: gas, laughing gas, nitrous

"It's a gas!" it is said, referring to anything in the way of fun, hilarity, and general giddiness. Nitrous oxide (nitrogen monoxide) may well be the source of that expression, for it is relatively harmless, -relatively legal, and superlatively mindblowing.

A colorless gas with a sweet taste and odor, nitrous oxide is an artificial compound of nitrogen and oxygen. Tanks are available to the medical profession, although fun-seekers everywhere have managed to obtain their own supplies. Once a tank of the stuff is obtained, it can be taken back for refills time and again with no problem. A large tank costs about $60, the gas for it another $60, and refills still another S60. Small quantities of whipped-cream propellant can be sniffed from upright aerosol containers, and pressurized pellets, similar to CO 2 cartridges, are also available.

Inhalation, which affects the brain most rapidly, is the only route for nitrous: Nitrous freaks find it much more efficient to fill large party or weather balloons with the gas, passing these ritually like joints, rather than battling each other for a turn at an unwieldy tank. Some sharers find that surgical tubing and clips attached to a tank enable everyone to sniff from the same source, but this is more involved and less efficient than the balloon method. Sniffing from aerosol cans is chancy and can result in complications such as death.

More and more dentists are discovering that nitrous makes patients not only willing, but enthusiastic. A gaseous tranquilizer, it sedates and creates an analgesic effect by changing the patient's mood and interpretation of pain. Sedated, the patient feels something he may or may not interpret as pain; but either way, he doesn't care. Some dentists don't use it because the equipment, incorporating a device that at mixes oxygen with nitrogen, is expensive. Although a few patients may experience anxiety or nausea, and painkillers such as Novocain still have to be administered, the placid feeling produced by the gas for most has generally desirable effects.

Nitrous has other medical uses beyond dentistry. In a Russian hospital, a Harvard cardiologist found tanks of nitrous next to each coronary patient's bed. A study published in the Journal of the American Medical Association confirmed the superiority of nitrous over the more traditional oxygen and morphine, now used for heart-attack pain. Used during childbirth, it is safe for both mother and baby.

Correctly used, it is always administered with 20 to 35 percent oxygen, necessary to prevent anoxia, or oxygen deprivation. Effects are almost immediate, beginning within fifteen to thirty seconds, remaining about one to three minutes, and totally out of the system within five to ten minutes. Repeated inhalation creates a continuous high. It is nonaddictive and nonallergenic, with very slight tolerance development after repeated or prolonged administration. No withdrawal symptoms occur, and nitrous may be used safely in conjunction with other narcotic agents, or local anesthetic injections.

Inhalation at moderate doses produces euphoria with a numbing of the body, dizziness, tingling in the fingers and toes, and buzzing or humming in the head. Warm sensations wash over the body and a crossover of the senses, such as hearing sights and seeing sounds, may occur. Sensations gradually diminish, with hearing dissolving to a constant, electronic-like throbbing. Nitrous can release subconscious material. Thus, revelations and insights may occur in a magnified or distorted fashion, similar to LSD visions. Transitory, they are soon erased until the next inhalation.

Depending on dosage, nitrous may have a short-term effect on memory, concentration, and sensory function. Feelings of floating, driving, or flying have been noted, and there is a general sense of detachment from the body. Properly used, it is one of the safest of all drugs:

Anesthetic in action, the gas affects the central nervous system, obliterating one's perception of pain. Rather than depressing the central nervous system, nitrous stimulates it, although no one is quite sure how. Scientists say the gas stimulates the brain electrically in a manner similar to LSD, affecting the metabolism of the brain cells. It does not break down chemically in the body; it enters and exits the lungs s in an unchanged state.

Oxygen deprivation is the chief danger of nitrous use. Sustained inhalation, unaccompanied by adequate oxygen, , may be rapidly followed by severe decerebration (braindeath), heart failure, pulmonary edema, or organic brain damage. Cyanosis, indicated by slow pulse, rise in blood pressure, twitching of the muscles, violent respiration which becomes increasingly shallow and irregular, and delirium, may accompany oxygen shortage. White-blood-cell count may drop and tissues may dry out, resulting in bronchial , irritation.

Nitrous oxide's side effects and dangers can be eliminated by taking simple safety precautions. Nausea may be avoided by refraining from eating -large meals before a nitrous trip. Keep the tank vertical and don't breathe straight from it, or you may freeze your lips and larynx. Don't attach the source of the gas to the nose or mouth, or undue pressure may, be exerted on the lungs by the force of the rushing; gas. Since it is important to breathe deeply -between hits to balance the oxygen level, not attaching the gas also ensures that you won't become unconscious from lack of oxygen. Don't fill up a small enclosed area, like a car or closet, with the gas, and don't stuff your head into a plastic bag full; of gas unless you want to suffocate.

Nitrous is one of those quasi-legal drugs whose medical use and distribution are monitored by federal regulations applied = to prescription drugs. Penalty for unapproved possession is imprisonment for not more than one year and/or a fine of up tŠ $5,000. If you're into concocting your oven illicit supply, - nitrous may be made by applying heat to ammonium nitrate crystals. This is not recommended unless you are a chemistry whiz.

Joseph Priestley, the discoverer of oxygen, also identified nitrous oxide in 1776, but never used it. Sir Humphrey Davy, in the same year, synthesized nitrous by exposing nitrous peroxide to iron, removing three of the four oxygen atoms, and all his inhibitions. A deep whiff of N 2O Davy , discovered, resulted in, a riotous state of excitement and glee. Naturally, he wanted to share this pleasure with his good friends, so the nitrous party was born. Prominent among the inhalers were Samuel Taylor Coleridge, Robert Southey, Josiah Wedgwood, and Peter Mark Roget (of thesaurus fame). This jolly group favored the effects of N20 O over those of alcohol. Davy noted that one of these effects was the alleviation of pain. In 1799. he proposed that nitrous be used during surgery, but no one took him seriously for another forty-five years.

At its inception, nitrous was a mere entertainment. Demonstrations; of "laughing gas" and another amusement, electricity, toured the country. Horace Wells, a dentist, attended one of these carnival acts put on by Gardner Quincy Colton in 1844, and had a flash: painless dentistry! His first demonstration in 1845 at Massachusetts General Hospital was a disaster. The patient came out of the gas too soon and screamed in pain-definitely a downer for Wells. However. use of nitrous spread, and today it enjoys: a dual reputation as pain repressant and pleasure producer-nothing to sniff at.