Subject sealing glasses

Holland and White l applied measured quantities of CS to the forearms of subjects under 4-cm-dlameter sealed glass covers. The dry powder produced erythema In 30 min when 20 mg or more was used. When 2 drops of saline solution was added, the amount required was 10 mg. Erythema was transient, fading out In 1 or 2 days with no after-effects. 

Many years later, a more detailed study of the subject was published by Root, Saeman, Harris, and Neill [16]. Using sealed glass ampoules heated by immersing them in oil of various temperatures, these authors reacted aqueous xylose solutions acidified by sulfuric acid, and measured... 

The term supercritical fluid is used to describe any substance above its critical temperature and pressure. The discovery of the supercritical phase is attributed to Baron Cagniard de la Tour in 1822 [3], He observed that the boundary between a gas and a liquid disappeared for certain substances when the temperature was increased in a sealed glass container. While some further work was carried out on supercritical fluids, the subject remained essentially dormant until 1964 when a patent was filed for using supercritical carbon dioxide to decaffeinate coffee. Subsequent major developments by food manufacturers have led to the commercialization of this approach in coffee production. The use of supercritical fluids in the laboratory was initially focused on their use in chromatography, particularly capillary supercritical fluid chromatography (SFC). However, it was not until the mid-1980s that the use of SFE for extraction was commercialized. 

An interesting intermediate version of the pyrolysis method has been proposed by Swann and Dux [12]. They pyrolysed a polymer in an evacuated sealed glass ampoide (a 50-mg sample was heated for 15 min), and the pyrolysis products were subjected to GC analysis after the ampoule had been broken in the carrier gas flow upstream of the column inlet. 

Subjecting 4-hydroxybenzaldehyde 29 (R = H) to 3-methyl-2-butenal (30) in the presence of pyridine in a sealed glass tube to MWI for 25 min yielded chromene 31 in 68% yield. Under similar conditions, the condensation of 2,4-dihydroxybenzalde-hyde 29 (R = OH) with 30 gave chromenes 32 and 33 in 49% and 12% yields, respectively (99BCJ259). 

Consider the design of a glass window for a vacuum chamber (Fig. 18.6). It is a circular glass disc of radius R and thickness f, freely supported in a rubber seal around its periphery and subjected to a uniform pressure difference Ap = 0.1 MPa (1 atmosphere). The pressure bends the disc. We shall simply quote the result of the stress analysis of such a disc it is that the peak tensile stress is on the low-pressure face of... 

The arrangement is then placed in a furnace, heated to 800°C, and the pressure decay test is repeated. The setup can be subjected to thermal cycles with pressure decay tests at room temperature and at 800°C. A good hermetic seal, however, will not show any pressure decay at a low pressure differential. The results of one series of tests using a glass composite material that has a glass transition temperature (Tg) of about 700°C, at 5 psi are shown in Figure 5.10. The combination of pressure and thermal cycle tests showed that the seal is capable of withstanding the pressure... 

Teflon sleeves are used to assure the vacuum tight connection between the ground joints subjected to heat. The checkers used clear-seal joints in all of the glass connections. 

Ring-seals of all kinds tend to be mechanically weak and sensitive to thermal shock. Tungsten-through-glass seals and pockets for thermocouples or conductivity probes are the most frequent instances of ring-seals on vacuum equipment, and these should never be subjected to extreme cold. 

Alternatively, an appropriate number of glass vials are filled to the proper level with sterilized WFI, following which the filled bottles are subjected to the lyophilization process. The processed bottles are then filled with a known volume of a sterile liquid medium, sealed, and incubated as described above. 

The subject of vacuum-line technique is approached here from the perspective of the novice user who may wish to construct a system in collaboration with a glassblower. The literature on vacuum technology [3-11] and glassblowing [12-17] is vast and there are many commercial firms that specialize in it. Within the past decade, newer components such as Teflon-glass needle valves, O-ring seals, and oil diffusion pumps have been introduced into vacuum systems. 

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