Laboratory scale, hazards

Also, pilot plant and laboratory scale anaerobic studies have demonstrated successful treatment of wastewaters of 5,000 to 50,000 mg/L GOD from corn chips containing soluble and colloidal corn starch and protein, cheese whey, organic chemicals, food, bakeiy, breweiy, paper mill foul condensate, paint, and numerous other hazardous anci non-hazardous materials. 

DesMarteau, D. D. et al., J. Amer. Chem. Soc., 1987, 109, 7194-7196 Fluorine is the most electronegative and reactive element known, reacting, often violently, with most of the other elements and their compounds (note the large MRH values quoted below). Handling hazards and disposal of fluorine on a laboratory scale are adequately described [1,2,3,4,5][6], and a more general review is also available [7], Safety practices associated with the use of laboratory- and industrial-scale fluorine cells and facilities have been reviewed [8], Equipment and procedures for the laboratory use of fluorine and volatile fluorides have been... 

Heat, and sometimes gas, transfer from the core of a bulk material, also influences auto-ignition and explosion. The concept of critical mass is not limited to nuclear explosives (though shape is also important). Some entries in this text, such as sodium chlorate, ammonium nitrate and ammonium perchlorate, have proved extremely destructive dining industrial storage by the tens of tonnes, but are incapable of explosion at the ten gramme scale. Many other entries are for hazards significant only beyond laboratory scale [1]. 

From these publications, workers interested in exploring the microwave technique perceived it to be simultaneously beneficial through increased rates, yet hazardous in the presence of flammable organic solvents. Subsequently, a vast body of work was carried out with domestic microwave ovens, but under solvent-free conditions and without recourse to sample mixing or temperature measurement. This continued across a broadening front on the laboratory scale. These and other developments in microwave chemistry have been reviewed extensively in journals, book chapters4-20 and in a recent monograph21. 

The liquid can be exploded by a detonator, though not by mechanical shock [1]. Use of propylene oxide as a biological sterilant is hazardous because of ready formation of explosive mixtures with air (2.8—37%). Commercially available mixtures with carbon dioxide, though non-explosive, may be asphyxiant and vesicant [1], Such mixtures may be ineffective, but neat propylene oxide vapour may be used safely, provided that it is removed by evacuation using a water-jet pump [2]. The main factors involved in the use and safe handling on a laboratory scale have been discussed [3]. The energy of decomposition (in range 340—500°C) has been measured as 1.114 kJ/g [4]. 

Although gas evolution is usually endothermic in open systems, and seldom a problem on laboratory scale, industrial batch reactors combine relatively far smaller vents with lower rupture pressures. This can give dangers with even endothermic evolutions. Exothermic gas evolving reactions readily become uncontrollable. A further hazard is nucleation and heating of saturated and supersaturated gas solutions when crystallisation of products occurs this is the cause of many reactions jumping... 

As the size of the vessel increases, the ratio becomes increasingly unfavorable. Thus, there is a critical value for D for which an exothermic reaction can easily be controlled on a laboratory scale and may be hazardous on a larger scale. 

The transformation of alcohols into aldehydes and ketones is of paramount importance in organic chemistry, both for laboratory-scale experiments and in the manufacturing processes (1). Unfortunately, the vast majority of the common oxidants have to be used at least in stoichiometric amount. Moreover, they are usually hazardous or toxic and generate large quantities of noxious by-products (2). Whilst many ecologically benign processes have been developed for the reduction of carbonyl derivatives (5), similar procedures have been far less investigated for the oxidation of alcohols (4). 

Questions are sometimes raised about the potential harmful effects of ultrasound produced by laboratory-scale devices. Available data indicates that airborne ultrasonic fields do not appear to be hazardous to humans. There are, in fact, no known physiological effects from airborne ultrasound. Ultrasonic sickness appears to be largely psychosomatic. 

Recycling of plastics is difficult, because of the content of the additives PBBs and PBDEs [27]. Pyrolysis of flame retardant material of printed circuit board and electronics components (laboratory scale) produces high amounts of brominated dioxins and furans (2,3,7,8-TeBDF, 29 pg/kg residue after quarts flask pyrolysis in N2/H2 atomosphere at 1100 °C) located in the condensed material. It was known that these plastics contain flame retardants to a maximum of 20 wt%. PBDEs can be extracted from plastics based on propyl-carbonate. The origin of brominated dioxins and furans detectable in propyl-carbonate extract is still to be investigated. Further recycling activities which process flame retarded plastics might produce hazardous products, an aspect that has to be investigated more closely [27]. 

Other methods for forming blends such as by evaporation of a solvent or by polymerization of a monomer in the presence of a polymer involve at least three components in the preparation process. Mixing in a common solvent followed by its removal is a convenient way of making blends on a laboratory scale, but has obvious commercial disadvantages due to the cost and difficulty of solvent recovery as well as the potential environmental hazards associated with handling large volumes of often toxic chemicals. In specific applications, however, such as membrane formation or paints and coatings where thin films are required, the use of solvents is unavoidable. 

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