Water baths, hazards

It must be borne in mind that in spite of the fact that the solvents have normal boiling points below 90-95°, they cannot always be completely removed by heating on a steam or water bath when they form part of mixtures with less-volatile liquids. Simple distillation may lead to mixtures with higher boiling points than the individual solvents, so that separation of the latter may not be quite complete. In such cases the distillation should be completed with the aid of an air bath (Fig. 77,5,3) or an oil bath the Are hazard is considerably reduced since most of the solvent will have been removed. 

Preparing peracetic acid by the action of hydrogen peroxide on acetic acid is as hazardous. If the temperature is too low, compounds accumulate and cause the medium to detonate. Using peracetic acid solution as an oxidant causes detonations when its concentration is too high or if evaporation is attempted. An accident happened during such an operation (see reaction below). The best way to eliminate this peracid at the end of the reaction is to heat it in a water bath at a temperature that should not exceed 50°C and under reduced pressure. 

Types of Process Equipment. Nitrations, as technical industrial processes, have evolved from batch-type operations using stoneware vessels and hand operations to automatically controlled continuous-type processes carried out in gleaming stainless-steel vessels. The high heats of reaction and dilution involved in nitration, originally absorbed by placing the stoneware vessels in a water bath, are now taken up by coils or jackets cooled by refrigerated brine. Controls have evolved from none at all to completely automatic,systems which may be so elaborate as to permit operation from remote locations. The idea of remote control has always appealed to the designer of equipment for the manufacture of hazardous, explosive compounds which often are the result of nitration processes. 

Water baths may become contaminated by the cultures that are incubated in them (201) therefore precautions are needed to prevent growth of organisms that can present a hazard or cause cross-contamination problems. Water baths used to inactivate or incubate hazardous substances should contain a disinfectant, such as chlorine bleach (0.8 ml per liter of water) or a phenolic detergent (8 ml per liter). The phenolic detei nt is preferred as it is less corrosive and more stable than chlorine (see Chapter 5). For chilled water baths, 70 percent propylene glycol is recommended (209, 479). Sodium azide should not be used as a bacteriostatic agent, as it creates a serious explosion hazard. 

Another potential hazard found in the laboratory is the water bath. This equipment, generally regarded as innocuous, can pose a safety hazard as the equipment ages. If the ground becomes faulty, and the heaters corrode sufficiently to expose the hot contacts of the heater, a severe shock hazard can develop. Recommendation as the equipment ages, check the continuity of the ground (plug to case) at frequent intervals. 

Methyl parathion can enter your body if you eat food or drink water containing it if you swim, bathe, or shower in contaminated water if you touch recently sprayed plants or soil if you touch contaminated soil near hazardous waste sites or if you breathe air that contains methyl parathion, such as near factories or recently sprayed farm fields (or in recent accounts of the illegal use of methyl parathion, if you breathe air or touch contaminated surfaces inside homes where methyl parathion has been used to kill insects). By any means of exposure, methyl parathion goes into your body quickly and gets into your blood. From your bloodstream, methyl parathion goes to your liver, brain, and other organs. Your liver changes some of methyl parathion to a more harmful chemical called methyl paraoxon. Both methyl parathion and methyl paraoxon can bind to enzymes of your nerves within minutes or hours. Your liver breaks down methyl parathion and methyl paraoxon into less harmful substances. These less harmful substances leave your body in urine within hours or days. For more information, see Chapter 3. 

Exposure to trichloroethylene can occur via the inhalation, oral, and dermal routes in people living in areas surrounding hazardous waste sites if evaporation occurs from contaminated soils or spill sites, or if contaminated water is ingested or used in bathing. Individuals who work in the vicinity of industries that use this substance may breathe trichloroethylene vapors or come into physical contact with spilled trichloroethylene. The group with the greatest likelihood for substantial exposure to trichloroethylene consists of those exposed to trichloroethylene in the workplace. 

Although human data are not extensive, the data suggest that dermal effects may be a concern for some humans exposed to trichloroethylene, particularly through bathing with contaminated water however, it is unlikely that exposure to trichloroethylene in the air or soil at hazardous waste sites would be irritating to human skin. Some people may develop immunological sensitivity to trichloroethylene which may manifest as a dermal response following inhalation, oral, or dermal exposure to trichloroethylene. 

Because the phosphates are readily absorbed through the skin and are hazardous from exposure by any route, prevention of poisoning includes avoiding contact with the bare skin and avoidance of inhalation of the chemicals. It is recommended also that workers change their clothes completely and bathe with soap and water after every use of this material. Particular caution is indicated on the part of pilots engaged in airplane spraying because of the effects of the organic phosphates on the eyes. Parathion presents special problems because of its translocation into the plant. 

Dibromoethane can enter your body after you eat or drink contaminated food and water. It can also enter your body through your skin when you bathe or swim in contaminated water. The 1,2-dibromoethane inside tiny soil particles may enter your body if you crush or eat contaminated soil. The chemical can enter your nose and lungs when you breathe air that contains 1,2-dibromoethane or when you shower with water that is contaminated. Near hazardous waste sites or near areas that once were farmed, the most likely way that you will be exposed is by drinking contaminated groundwater. 

A Individuals residing near hazardous waste site Hazardous waste site Volatile chlorinated solvents Ground water used for drinking, bathing, cooking Ingestion, inhalation, dermal contact... 

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