Pressure cookers

Technically, the chemist could avoid the complex glassware apparatus of this procedure for a more crude approach [104]. This report shows some dudes de-methylating an amphetamine with concentrated HCI in a pressure cooker. A similar approach with good yields was also employed in ref. 83 and should work as well or better on guaiacol. Hydroiodic acid or hydrobromic acid will work better than hydrochloric acid but, you know, whatever floats the chemist s boat. To do this the chemist can just plain reflux HI or HBr with the guaiacol for a few hours and process as before or she can use HI, HBr or HCI and place the reactants in a pipe bomb for a few hours. 

Curing can be performed in several devices heated mold (Figure 1-13), hot press (heated plates that are forced together), and an autoclave which is essentially a very large version of an ordinary kitchen pressure cooker as in Figure 1-21. 

At sea level, (he barometric pressure is 760 mm Hg. Calculate the difference in the normal boiling point for water boiled in an open pot and water boiled in a pressure cooker set for 1.75 atm. (For water, AHnp =... 

It is recommended to autoclave glass dishes and medium separately. If your dishes are autoclaveable, you may dispense the agar into the dish and then autoclave it. In this case it is best to cool the dishes in the autoclave or in the pressure cooker to reduce the amount of water that will condense on the cover of the dish. 

Boiling occurs at a temperature higher than the normal boiling point when the pressure is greater than 1 atm, as it is in a pressure cooker. In this case, a higher temperature is needed to raise the vapor pressure of the liquid to the higher pressure. Boiling occurs at a lower temperature when the pressure is less than 1 atm, because now the vapor pressure matches the external pressure at a lower temperature. At the summit of Mt. Everest—where the pressure is about 240 Torr—water boils at only 70°C. 

How would the boiling point change if this 2. Explain what happens in a pressure cooker,... 

Notes CA98°C, heating tissue sections in 0.05 % citraconic anhydride at 98° C for 45 min CAPC, heating tissue sections in 0.05% citraconic anhydride in a plastic pressure cooker using microwave oven for 30 min Low pH, heating tissue sections in acetic buffer of pH 1-2 for shorter time as described in the text Citrate, conventional citrate acid buffer 0.01 M at pH 6.0 with same heating condition of a plastic pressure cooker described above. 

Another aspect to consider is that performance of HIAR within an automated staining instrument can add considerably to laboratory cost compared to performing manual HIAR off-line with devices such as pressure cookers, vegetable steamers, or microwave ovens.19 In addition, off-line HIAR methods... 

Taylor CR, Shi S-R, Chen C, et al. Comparative study of antigen retrieval heating methods microwave, microwave and pressure cooker, autoclave, and steamer. Biotech. Histochem. 1996 71 263-270. 

Other heating equipment. Autoclave used for sterilization can be used to achieve superheating condition at 120°C. For higher temperature heating, a domestic pressure cooker, or a plastic steamer may be used. Some commercial laboratory pressure cookers have been designed for AR-IHC with controlled temperature. A water bath can be used to achieve lower temperature heating condition. 

The hermeticity of the end seals of the capacitor. No joint is one hundred percent perfect, and some evaporation will take place slowly over time. We see the need to pick a vendor with a high (and consistent) quality. Yes, in principle, we could try to seal the capacitor totally, say by immersing it in a bath of epoxy-resin/ superglue for example But such capacitors are designed to vent under high pressure (much like a pressure cooker). However, I must tell you that despite all that safety chatter, I have seen some capacitors explode furiously. Remember, it once happened to me in Bombay ... 

Plan (1) Use the Clausius-Clapeyron equation to calculate the steam temperature in the pressure cooker. 

Why does water take longer to heat in a pressure cooker than in an open pan ... 

A pressure cooker is a sealed cooking pan. Being sealed, as soon as boiling occurs, the pressure of steam within the pan increases dramatically, reaching a maximum pressure of about 6 x /A, causing the final boiling temperature to increase (see Fig. 5.12 on p. 200). Unlike other pans, the internal volume is fixed and the pressure can vary the pressure in most pans is atmospheric pressure ( p°), but the volume of the steam increases continually. 

The heat capacity of the contents in a pressure cooker is Cv because the internal volume is constant. By contrast, the heat capacity of the food or whatever inside a conventional pan is Cp. The water is a pressure cooker warms slower because the value of Cp is always smaller than Cv- And being smaller, the temperature increases faster per unit input of energy. 

See p. 199 to see why a pressure cooker can cook faster than a conventional, open pan. 

The value of Cv is 11 per cent higher than Cp, so the water in the pressure cooker will require 11 per cent more energy than if heated in an open pan. 

A pressure cooker is a sealed saucepan in which food cooks faster than it does in a simple saucepan - where simple , in this context means a saucepan that is open to the air. A pressure cooker is heated on top of a cooker or hob in the conventional way but, as the water inside it boils, the formation of steam rapidly causes the internal pressure to increase within its sealed cavity see Figure 5.11. The internal pressure inside a good-quality pressure cooker can be as high 6 atm. 

Figure 5.11 A pressure cooker enables food to cook fast because its internal pressure is high, which elevates the temperature at which food cooks...

Figure 5.12 Phase diagram to show how a pressure cooker works. Inset, applying a high pressure from pe to P2 causes the boiling temperature of the water to increase from temperature 100 °C to T2...

Having qualitatively discussed the way a pressure cooker facilitates rapid cooking, we now turn to a quantitative discussion. The Clapeyron equation, Equation (5.1), would lead us to suppose that dp oc dT, but the liquid-gas phase boundary in Figure 5.12 is clearly curved, implying deviations from the equation. Therefore, we require a new version of the Clapeyron equation, adapted to cope with the large volume change of a gas. To this end, we introduce the Clausius-Clapeyron equation ... 

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