Heating glassware

Distinguish absorption from adsorption. When you heat glassware in a drying oven, are you removing absorbed or adsorbed water ... 

The best replacement for borosilicate glassware is stainless steel. Stainless steel takes the heat, won t break, and, most importantly, is about as resistant to chemical degradation as the chemist can hope to find. For those items that won t be subjected to direct heat there can be some steel/metal or steel/plastic hybrids. In figure 3 is shown how flasks of any size can be made with two stainless steel mixing bowls welded together. Also shown is the vacuum adaptor and condenser. For the condenser only the inner pipe need be steel. The outside pipe can be copper or something. As for the other components of a distillation set up, well, they are made just as they look. 

Batch vs Continuous Reactors. Usually, continuous reactors yield much lower energy use because of increased opportunities for heat interchange. Sometimes the savings are even greater in downstream separation units than in the reaction step itself Especially for batch reactors, any use of refrigeration to remove heat should be critically reviewed. Batch processes often evolve Httle from the laboratory-scale glassware setups where refrigeration is a convenience. 

For heating baths, see Table 4. For distillation apparatus on a micro or semi-micro scale see Aldrich and other glassware catalogues. Alternatively, some useful websites for suppliers of laboratory glassware are www.wheatonsci.com,www.sigmaaldrich.com and www.kimble-kontes.com. 

Chemical reaction hazards must be considered in assessing whether a process can be operated safely on the manufacturing scale. Furthermore, the effect of scale-up is particularly important. A reaction, which is innocuous on the laboratory or pilot plant scale, can be disastrous in a full-scale manufacturing plant. For example, the heat release from a highly exothermic process, such as the reduction of an aromatic nitro compound, can be easily controlled in laboratory glassware. Flowever,... 

A reaction was believed to be thermally neutral, as no rise in temperature was observed in the laboratory. No cooling was provided on the pilot plant, and the first batch developed a runaway. Fortunately the relief valve was able to handle it. Subsequent research showed that the reaction developed 2 watts/kg/°C. Laboratory glassware has a heat loss of 3-6 watts/kg/°C, so no rise in temperature occurred. On the 2.5-m3 pilot plant reactor, the heat loss w as only 0.5 watt/kg/°C [21]. Reference 22 lists heat losses and cooling rates for vessels of various sizes. 

All glassware is oven-dried. The dropping funnel is wrapped with heating tape, and a thermometer is inserted between the funnel and the tape. 

Dry heat sterilisation is used for equipment that can withstand high temperature and dry heat but cannot withstand wet or steam autoclave. This method is often used for glassware as it dries and sterilises in one operation. The pipets must be wrapped in dustproof aluminum foil or placed in metal pipette cans. The can lids are removed during heating and replaced after sterilisation, that is before any dust can get in the can. Disposable items are not recommended for dry heat sterilisation. This method may only be good for permanent reusable glass pipettes. 

Normal laboratory glassware must first be washed and cleaned. It has to be rinsed with deionised water. The clean glassware is sterilised in an oven set at 200 °C for 1 1 hours. It is suitable to cover glassware with aluminum foil to maintain aseptic conditions after removing the glassware from the oven. If aluminum foil is not available, special heat-resistant wrap paper can be used. The sterile glassware must be protected from the air, which has micro-flora, or any contaminants. Avoid the use of any plastic caps and papers. Detach any labelling tape or other flammable materials, as they are fire hazards. 

The glassware was dried in an oven at 120° for 2 hours and assembled quickly while still hot. It is possible and occasionally desirable in humid climates to dry the apparatus after assembly by heating its accessible parts with a low flame from a Meaker burner while flushing it with a stream of argon, but this operation is normally unnecessary. 

Which of these pieces of laboratory glassware should NEVER be heated with a Bunsen burner ... 

Dry heat is widely used to sterilize glassware and equipment parts in manufacturing areas for parenteral products. It has good penetration power and is not as corrosive as steam. However, heat-up time is... 

Breakage of glassware allowed 92% sulfuric acid into a heating bath containing hot Synperonic NX (nearly anhydrous ethoxylated nonylphenol, a liquid surfactant). Hydrolysis of the latter lowered the flashpoint and the bath ignited (possibly from formation of dioxane, flash point 12°C). 

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