Insulated container

The main use of lead metaborate is in glazes on pottery, porcelain, and chinaware, as weU as in enamels for cast iron. Other appHcations include as radiation-shielding plastics, as a gelatinous thermal insulator containing asbestos fibers for neutron shielding, and as an additive to improve the properties of semiconducting materials used in thermistors (137). 

Some inorganic nonaqueous solvents can be used in systems operable at near room temperature, eg, thionyl chloride others, however, require special handling, eg, Hquid ammonia, which must be used below its boiling point of —33° C in a thermally insulated container and in an inert atmosphere. 

Smaller quantities of liquid nitrogen are shipped in liquid cylinders, which are pressurized stainless steel vacuum-insulated containers with capacities of 160—180 L of hquid nitrogen, producing 100—120 (3800—4600 SCF) gaseous nitrogen when vaporized. Moderate quantities of high pressure gaseous... 

They may lead to deterioration of the insulation of the insulating container due to condensing of the metal vapour on the inner surface of the container (more in iransvei se magnetic field type breakers). 

Use only labelled, insulated containers designed for cryogens, i.e. capable of withstanding rapid changes and extreme differences in temperature, and fill them slowly to minimize thermal shock. 

Consideration must be given to possible equipment corrosion from such external sources as a corrosive atmosphere, spills, insulation, or gland leakage. For example, insulation containing trace quantities of chlorides can cause stress corrosion failure of 18-8 stainless steel vessels and piping. ... 

The transport of perishables by air does not require mechanical refrigeration, as low temperatures prevail at the heights flown. Fresh vegetables and flowers need to be protected from freezing, and produce will usually be in insulated containers. A feature of this traffic is the prompt and speedy handling at the airports. Coldrooms are provided at some airports to store produce immediately before and after transit. Solid carbon dioxide ( dry ice ) is used for shortterm cooling of airline passenger meals. 

Equal masses of liquid A, initially at 100°C, and liquid B, initially at 50°C, are combined in an insulated container. The final temperature of the mixture is 80°C. All the heat flow occurs between the two liquids. The two liquids do not react with each other. Is the specific heat of liquid A larger than, equal to, or smaller than the specific heat of liquid B ... 

A calorimeter Is a device used to measure heat flows that accompany chemical processes. The basic features of a calorimeter include an Insulated container and a thermometer that monitors the temperature of the calorimeter. A block diagram of a calorimeter appears in Figure 6-15. In a calorimetry experiment, a chemical reaction takes place within the calorimeter, resulting in a heat flow between the chemicals and the calorimeter. The temperature of the calorimeter rises or falls in response to this heat flow. 

Constant-pressure calorimetry requires only a thermally insulated container and a thermometer. A simple, inexpensive constant-pressure calorimeter can be made using two nested Styrofoam cups. Figure 6-16 shows an example. The inner cup holds the water bath, a magnetic stir bar, and the reactants. The thermometer is inserted through the cover. The outer cup provides extra thermal insulation. 

The tendency, for economic reasons, to store it in very large insulated containers. 

A 10-carbon oxime at 60°C was stored in an insulated container, and within 24 h the temperature had risen to 125°C, possibly owing to an exothermic Beckmann rearrangement to an amide. Application of cooling prevented a thermal runaway. 

The process of evaporation is an endothermic one it requires energy. If evaporation occurs from an uninsulated container, this energy is obtained from the surroundings, through the walls of the container. However, if the evaporation occurs from an insulated container, the only source of the needed energy is the liquid that is evaporating. Therefore, the temperature of the liquid decreases. 

So that there is no gain nor loss of heat, thermochemical reactions that are called adiabatic are carried out in well-insulated containers called calorimeters. The reactants and products in the calorimeter are called the chemical system. Everything else is called the surroundings, and includes the air above the calorimeter, the water in the calorimeter, the thermometer and stirrer, etc. 

Typically, it is best to move the sample from the field to the laboratory as quickly as possible and to minimize storage time in the laboratory. A container, often insulated, is commonly used for containing samples during transport. Using an insulated container allows one to maintain a desired temperature between field and laboratory and to isolate the samples from possible con-tamination.Table 7.1 shows the container, preservative, and storage times used for various types of common samples. 

Cooling. Some formulas call for external cooling of the reaction. These temperatures should be followed exactly or the product intended may evolve into something completely different. To aid you in cooling, I have listed the following substances to be mixed and the temperature reductions created by them. If carried out in an insulated container these mixtures will hold a more even temperature for a much longer period. Those little Playmate lunch boxes make perfect insulated containers. 

Place vials in an insulated container and store at -80 °C overnight (see Note 3). 

A basic method for determining the energy change involved with many chemical processes is calorimetry. A calorimeter is an insulated container used to carry out a chemical process. A thermometer is used to measure temperature changes that take place during the process. A simple constant-pressure calorimeter is shown in Figure 10.3. This type of calorimeter derives its name from the fact that it is open to the atmosphere and the pressure remains constant during the process. Constant-pressure... 

A 375 g plug of lead is heated and placed in an insulated container filled with 0.500 L of water. Prior to the immersion of the lead, the water is at 293 K. After a time, the lead and the water assume the same temperature, 297 K. The specific heat capacity of lead is 0.127 J/(g K), and the specific heat capacity of water is 4.18 J/(g K). How hot was the lead before it entered the water (Hint You ll need to use the density of water.)... 

Figure 6. Insulated containers can protect instrumentation against mechanical damage, weather, and dust.

An alternative method of calorimetry that gives less accurate results, but is simpler in concept, uses only a single insulated container and a thermometer. Temperature changes in the calorimeter are brought about by adding hot (or cold) objects of known weight and temperature. Calculations are based on the principle that the heat lost by the added hot object is equal to that gained by the water in the calorimeter and the calorimeter walls. This simple approach is illustrated in the next two problems. 

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