Nitrous oxide cylinders

Nitrous Oxide. Nitrous oxide, described by Priesdy in 1772, was first used to reHeve severe dental pain in the latter part of the 18th century. Sometime in the mid-1800s N2O was successfully used as an anesthetic, and its widespread usage coincided with the development of anesthesia machines. Nitrous oxide is a nonflammable, colorless, odorless, and tasteless gas that can exist as a Hquid under pressure at room temperature. It is normally stored in cylinders. However, it supports combustion. 

A nitrous oxide cylinder should not be used after the regulator gauge has dropped to a reading of 100psi (6860kNm-2). 

A man habitually enjoyed the euphoric effects of inhaling whiffs of nitrous oxide in seclusion, and kept a cylinder of the gas in his sedan for that purpose. He decided to spray the faded car seats with an aerosol can of vinyl dressing (propanc/butanc propellant) with the windows closed. Then he had a whiff of gas from the briefly opened cylinder, and settled back to enjoy the euphoria and a cigarette. He was lucky to survive the resulting explosion of the fuel/oxidant mixture in a closed vessel [2],... 

Nitrous oxide (N2O 99.0 %) and helium (He 99.999 %) from commerical cylinders were purified through a dry ice-methanol trap to remove water vapor. 

The reactor used consists of a Pyrex glass tube containing 260.6 g catalyst and was immersed in an oil bath. The temperature of the catalyst bed remained constant within + 0.1°C of the desired temperature. Oxygen (0 99.9%), nitrogen (N 99.9%), nitrous oxide (N ,0 99.99%), carbon dioxide (99.9%) and helium (He 99.999%) from commercial cylinders were purified through a dry ice-methanol trap to remove water vapor. 

The sources of acetylene, nitrous oxide, and sometimes air are usually steel cylinders of the compressed gases purchased from specialty gas or welders gas suppliers. Thus, several compressed gas cylinders are usually found next to atomic absorption instrumentation and the analyst becomes involved in replacing empty cylinders with full ones periodically. Safety issues relating to storage, transportation, and use of these cylinders will be addressed in Section 9.3.7. The acetylene required for atomic absorption is a purer grade of acetylene than that which welders use. 

Therefore, the pressure gauge can be used as a measure of the amount of oxygen left in the cylinder. The reason we cannot use a nitrous oxide cylinder pressure gauge in the same way is that these cylinders contain both vapour and liquid and so the gas laws do not apply. 

Parenteral 1, 5 mg/mL for injection in 1, 2, 5, 10 mL vials Oral 2 mg/mL syrup for children Nitrous oxide (gas, supplied in blue cylinders)... 

IV) Nitrous Oxide was procured in carload lots of 200 50 lb cylinders. It was USP grade, free of impurities to the iowest practical amt and which were designated on the... 

Having a high critical temperature, nitrous oxide can exist as a liquid at room temperature (5.01 MPa at 294 K). Commonly, it is stored and transported in the liquefied state under pressure in steel cylinders or refrigerated tanks. 

Companies in both America and the United Kingdom succeed in producing compressed and liquid nitrous oxide in cylinders. 

Nitrous oxide is synthesized, or produced, by heating ammonium nitrate (NH4N03) and then condensing out the water and filtering impurities. The gas is then compressed and turned into liquid for storage in tanks, cylinders, or cartridges. 

Medical grade nitrous oxide is a prescription drug sold as a compressed liquid in cylinder tanks. Its buyer requires appropriate credentials to obtain it (which are governed by state law). Nitrous oxide used for other legitimate applications, such as manufacturing and auto racing, is often sold in a denatured form. Denatured nitrous contains chemicals that render it unfit for human consumption. 

Also, working with any compressed gas may be dangerous. Although nitrous oxide itself is not flammable, the pressurized contents can explode and cause serious injury if a gas tank or cylinder is improperly stored, or is dropped, knocked over, or punctured. 

An Entonox cylinder has a total pressure of 137 bar. The cylinder is stored at 0.0°C, and a mixture of 80% N20 and 20% 02 liquefies in the bottom of the cylinder. The vapor pressure of the nitrous oxide under these conditions is 17,000 torn This means that, as long as this liquid phase is present in a closed container, the partial pressure of nitrous oxide remains 17,000 torn... 

A second problem with nitrous oxide was its property of cooling dramatically when allowed to expand very rapidly on going from high pressure to low pressure. This resulted frequently in ice formation on the cylinder head, and poor gas flow stability. To avoid the consequential loss in precision, cylinder heads were often warmed, or a ballast tank at an intermediate pressure could be used as a stabilizer.9 Most modern AAS instruments employ quite high oxidant pressures and flow rates in the interests of safety, in spite of the greater cost, and this problem is less common than it used to be. 

Fuel and air or nitrous oxide flow stabilities must be adequate for good precision. Intermediate balast tanks help to smooth out fluctuations caused by compressors.3 As mentioned in Chapter 2, section 5, nitrous oxide cools when it is subjected to a sharp pressure drop, which results in cooling of the cylinder head, and sometimes in instability. The effect is not as important if the nitrous oxide operating pressure... 

Nitrous oxide is contained and transported in its liquid phase in high-pressure gas cylinders or in liquid cylinders. It is transported as a liquefied compressed gas under high pressure in cylinders and at lower pressures and reduced temperatures in refrigerated cargo tanks and insulated portable tanks. Nitrous oxide is stored in a foam-insulated tank accompanied by a refrigeration unit, which is similar to the tank used for carbon dioxide. 

Note The following tests are designed to reflect the quality of Nitrous Oxide in both its vapor and its liquid phases, which are present in previously unopened cylinders. Reduce the sample gas cylinder pressure with a regulator. Withdraw the samples for the tests with the least possible release of sample gas consistent with proper purging of the sample apparatus. Measure the gases with a gas volume meter downstream from the detector tubes to minimize contamination of or change to the samples. The detector tubes called for in certain tests are described at the end of Solutions and Indicators. 

A. With the cylinder temperatures the same and maintained between 15° and 25°, concomitantly read the pressure of the cylinder of sample gas and of a cylinder of 99.9% Nitrous Oxide certified standard (available from most suppliers). 

Note Do not use the Nitrous Oxide certified standard if its cylinder has been depleted to less than half of its full capacity. 

The pressure of the sample gas cylinder is within 50 psi of that of the Nitrous Oxide certified standard cylinder. 

A strongly reducing fuel-rich nitrous oxide—acetylene flame is superior to other flames for sensitivity and freedom from interferences. Optimisation of burner height is important as absorption signal is fairly dependent on observation height. In aqueous systems interference from calcium has been controlled by the addition of aluminium or Na2S04. Reduced sensitivity has been reported in the presence of acetone vapour from depleted acetylene cylinders. 

Today, nitrous oxide is available in many dentists offices. Realizing that people like to get high on it, some dentists give nitrous oxide even for routine procedures such as cleaning teeth. A fair number of tanks of the gas regularly disappear from hospitals and medical supply houses to find their way into the homes of recreational users. Many more people obtain smaller cylinders of the gas from restaurant suppliers, who use it to pressurize instant whipped cream cans. Some people even buy cans of instant whipped cream and attempt to get the gas out of the cans without the cream. Balloons of nitrous oxide have been offered for sale at some rock concerts. 

---