Nitrous oxide, safety

Safety provisions have proven highly effective. The nuclear power industry in the Western world, ie, outside of the former Soviet Union, has made a significant contribution of electricity generation, while surpassing the safety record of any other principal industry. In addition, the environmental record has been outstanding. Nuclear power plants produce no combustion products such as sulfuric and nitrous oxides or carbon dioxide (qv), which are... 

Many gases dissolve in fats and make good propellants. However, most are flammable or toxic, or they react with the fats. Other possible propellants, such as the propane used in hairsprays or in Freon, also cause intoxication when they dissolve in the fats around nerve cells. These substances are not used, since their flammability, safety, cost, or taste makes them less desirable than nitrous oxide for spray cans of whipping cream. 

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. 

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. 

Today we have sophisticated lab equipment to help us analyze the products of reactions. In the past, when such equipment was not available, chemists sometimes jeopardized their safety and health to determine the products of the reactions they studied. Sir Humphry Davy (1778-1829), a contributor to many areas of chemistry, thought nothing of inhaling the gaseous products of the chemical reactions that he carried out. He tried to breathe pure C02, then known as fixed air. He nearly suffocated himself by breathing hydrogen. In 1800, Davy inhaled dinitrogen monoxide, N20, otherwise known as nitrous oxide, and discovered its anaesthetic properties. What is nitrous oxide used for today ... 

Water is also included in the table to make one point— the solvent that we are all most familiar with is a poor candidate from both engineering and safety standpoint. The critical temperature and pressure are among the highest for common solvents. Ammonia is very unpleasant to work with since a fume hood or other venting precautions are needed to keep it out of the laboratory atmosphere. One of the alternative fluids of potential interest is nitrous oxide. It is attractive since it has molecular weight and critical parameters similar to carbon dioxide, yet has a permanent dipole moment and is a better solvent than carbon dioxide for many solutes. There are evidences of violent explosive reactions of nitrous oxide in contact with oils and fats. For this reason, nitrous oxide should be used with great care and is not suitable as a general purpose extraction fluid. 

Although airway conductance may be reduced by nitrous oxide, respiratory depression is unlikely after short-term exposure (8). The respiratory safety of nitrous oxide inhalation in children has been confirmed (9). 

Ammonium Nitrate, NH4N03.—See p. 13 for manufacture and properties. Its main use is for safety explosives, sporting powders, fireworks, etc. Much is used for the preparation of nitrous oxide, laughing gas. ... 

Occupational Safety and Health Guideline for Nitrous Oxide. Occupational Safety and Health Administration. http //www.osha.gov/SLTC/healthguidelines/nitrousoxide/ recognition.html (accessed on October 20, 2005). 

It is important to emphasize some aspects of safety. Cylinders of fuel and oxidant gases must be fastened to a wall or laboratory bench. The exhaust gases have to be channelled through an adequate ventilation system and released into the atmosphere. In some cases (e.g. when employing nitrous oxide) the exhaust gases are toxic. Special care has to be exercised when lighting and extinguishing the flame. 

Trace-gas analysis must be performed to guarantee the efficacy of the scavenging system. The National Institutes of Occupational Safety and Health (NIOSH) recommends that trace levels of nitrous oxide must be maintained at or below 25 ppm time-weighted average and that halogenated anesthetic agents remain below 2 ppm. 

It is possible to feed explosives and chemical agents simultaneously. These are then, as all other organics, oxidised to carbon dioxide, water, nitrous oxides and mineral salts. The system has been praised in several publications for its built-in safety and environmental compatibility. 

Even though the extraction efficiency for some analytes can be increased by change of extraction fluid, carbon dioxide is by far the most common compound used (98% of all applications). It has low critical parameters, it is nonexplosive, nontoxic, and environmentally benign. Alternatives have been proposed such as alkanes and freons but they have never been widely accepted due to health and safety risks for the former and ozone depletion by the latter. One of the few competitors to carbon dioxide is nitrous oxide, however, it might cause explosion in contact with high amounts of organic material. Supercritical carbon dioxide has a polarity similar to that of n-hexane, and consequently for the extraction of more polar analytes an organic modifier such as methanol or acetonitrile (1-5%) has to be added to increase the polarity (see the section Modifiers ). To maintain supercriticality for two-component fluids, somewhat different conditions have to be applied, but normally there is no problem at the conditions under which SFE is normally carried out. 

Davy, Sir Humphry (1778-1829) A chemist, teacher, and inventor born in England, Davy began conducting scientific experiments as a child. As a teen he worked as a surgeon s apprentice and became addicted to nitrous oxide. He later researched galvanism and electrolysis, discovered the elements sodium, chlorine, and potassium, and contributed to the discovery of iodine. He invented the Davy safety lamp for use in coal mines, was a founder of the Zoological Society of London, and served as president of the Royal Society. 

SB-6 Nitrous Oxide Security and Control. This safety bulletin is an alert to manufacturers, repackagers, distributors, and users of nitrous oxide for medical and commercial industrial purposes. It warns of the misuse and abuse of nitrous oxide so that effective steps can be taken to prevent theft or improper use (2 pages). 

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