Precautions ammonia

The conversion of a diazo ketone to an acid amide may be accomplished by treating a warm solution in dioxan with 10-28 per cent, aqueous ammonia solution containing a small amount of silver nitrate solution, after which the mixture is heated at 60°-70° for some time. Precautions should be taken (by use of a. safety glass shield) when heating mixtures containing ammoniacal silver nitrate. 

Silver fluoride forms explosive adducts with ammonia (qv) (5,6), and therefore all of the reactions involving Hquid or gaseous ammonia should be carried out with extreme precautions. 

Precautions must be taken to prevent ammonia from coming in contact with the quinone before the desired time. The dropping funnel is loosely stoppered, and the flask containing the remainder of the solution is well stoppered. 

This book briefly reviews ammonia synthesis, its importance in the chemical process industry, and safety precautions. This case study is integrated into several chapters in the text. See the Introduction for further details. 

Precautions also have to be instituted to protect against the inherent properties of the cylinder contents, e.g. toxic, corrosive, flammable (refer to Table 8.1). Most gases are denser than air common exceptions include acetylene, ammonia, helium, hydrogen and methane. Even these may on escape be much cooler than ambient air and therefore slump initially. Eventually the gas will rise and accumulate at high levels unless ventilated. Hydrogen and acetylene can form explosive atmospheres in this way. 

Freeder, B. G. et al., J. Loss Prev. Process Ind., 1988, 1, 164-168 Accidental contamination of a 90 kg cylinder of ethylene oxide with a little sodium hydroxide solution led to explosive failure of the cylinder over 8 hours later [1], Based on later studies of the kinetics and heat release of the poly condensation reaction, it was estimated that after 8 hours and 1 min, some 12.7% of the oxide had condensed with an increase in temperature from 20 to 100°C. At this point the heat release rate was calculated to be 2.1 MJ/min, and 100 s later the temperature and heat release rate would be 160° and 1.67 MJ/s respectively, with 28% condensation. Complete reaction would have been attained some 16 s later at a temperature of 700°C [2], Precautions designed to prevent explosive polymerisation of ethylene oxide are discussed, including rigid exclusion of acids covalent halides, such as aluminium chloride, iron(III) chloride, tin(IV) chloride basic materials like alkali hydroxides, ammonia, amines, metallic potassium and catalytically active solids such as aluminium oxide, iron oxide, or rust [1] A comparative study of the runaway exothermic polymerisation of ethylene oxide and of propylene oxide by 10 wt% of solutions of sodium hydroxide of various concentrations has been done using ARC. Results below show onset temperatures/corrected adiabatic exotherm/maximum pressure attained and heat of polymerisation for the least (0.125 M) and most (1 M) concentrated alkali solutions used as catalysts. 

A mixture of sodamide, bromoanisole, and l-methoxy-2-methyl-l-(trimethylsilyl-oxy)-l-butene were reacted at room temperature at a 50 millimolar scale. After some two horns, with slight emission of ammonia, the reaction suddenly became exothermic, with violent gas emission and on one occasion a fire. This was a modest scale-up of a literature procedure for synthesis of 2-alky lbenzoic acids, via a benzyne intermediate. It is advised that this reaction be employed only on smaller scale, with safety precautions. The reaction must pass through a benzocyclobutane intermediate, this, or another, high energy species might accumulate and then decompose. 

During the reductive cleavage of cyclopolyenes with potassium in liquid ammonia, the intermediate anionic species are quenched with iodine-pentane mixtures. The possibility of formation of explosive nitrogen triiodide and the need for precautions are stressed. 

In a 2-1. round-bottomed flask are placed, in the order mentioned, 50 g. (1 mole) of 98% sodium cyanide in 100 ml. of water, 58.9 g. (1.1 moles) of ammonium chloride in 140 ml. of lukewarm water (about 35°), and 134 ml. (2 moles) of aqueous ammonia (sp. gr. 0.90). The mixture is shaken while 120 g. (1 mole) of acetophenone in 300 ml. of 95% ethyl alcohol is added. The flask is stoppered with a rubber stopper, which is wired in place (Note 1), and is then immersed in a water bath maintained at 60°. The flask is shaken from time to time, and a homogeneous solution results within half an hour. The reaction mixture is heated for 5 hours at 60°, then well cooled in an ice-water mixture, and poured, with precautions (under a well-ventilated hood), into a 5-1. round-bottomed flask which is immersed up to the neck in an ice-water mixture and which contains 800 ml. of concentrated hydrochloric acid (sp. gr. 1.18-1.19). The reaction flask is rinsed with two 25-ml. portions of water, which are added to the hydrochloric acid solution. The solution of the aminonitrile is satu-... 

Contaminated clothing or bed linen could also spread the virus. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Disinfectants such as bleach and quaternary ammonia can be used for cleaning contaminated surfaces. 

Note also that ammonium sulfate is absent from the recommended binding buffer formulations despite its general popularity in the field. Ammonium ions become fully titrated at alkaline pH and convert to ammonia gas. Buffer pH may become unstable as a result and causticity of the free ammonia may partially hydrolyze the proteins in a sample, creating a source of assay variability.617 18 At small buffer volumes used for analytical applications, liberated ammonia gas may not be a significant health hazard, but precautions may still be necessary to meet regulations. For all these reasons, ammonium salts are best avoided at alkaline pH. 

Analyses of ambient air samples have thus far failed to detect the presence of sulfuric acid. However, considerable quantities of ammonium sulfate salts have been detected. One possible explanation is that sulfuric acid aerosol trapped on a filter is converted to ammonium salts by reaction with ammonia in the air pulled through the filter. A laboratory generated sulfuric acid aerosol collected on a Fluoropore filter was placed in a filter holder. Arbitrarily selected suburban and urban air was passed through the filter at a rate or 30 liters/minute for approximately one hour. In every case > 95% of the sulfuric acid was apparently converted to ammonium salts of sulfate. A strict material balance was not performed. A blank sample of laboratory generated sulfuric acid aerosols was transported to and from the field with proper precautions. Less than 5% conversion of the sulfuric acid to ammonium sulfate was observed for this sample. 

After about fifteen minutes, the theoretical amount of freshly distilled M-butyl nitrite (95 g. for every 100 g. of phenylhydroxylamine) is added slowly through a dropping funnel (Note 3). The addition of butyl nitrite usually requires about one hour (Note 4), during which time the stream of ammonia gas is continued in order that ammonia may always be in excess. If this precaution be not observed, a colored product will result. The temperature of the reaction mixture should be maintained below xo° and this may be done best by controlling the rate at which the butyl nitrite is added. An appreciable rise in tem-... 

It is found that 75 per cent of the ether and 95 per cent of the butyl alcohol used may be recovered, and that one man, working six to seven hours, is able to prepare 800 g. of cupferron. The recovered ether may be used over again, provided the following procedure is followed The phenylhydroxylamine is dissolved in a little fresh ether, the solution cooled and treated with ammonia, then the recovered ether added. This precaution is necessary owing to the presence of some butyl nitrite in the recovered ether. 

---