Glasses, sealing

Glasses are very well suited for the production of mechanically reliable, vacuum-tight fusion seals with metals, ceramics, and mica. Some particularly favorable properties are the viscosity behavior of glass and the direct wettability of many crystalline materials by glasses. As a result, the production technology for such seals is characterized by uncomplicated procedures with few, easily manageable, well-controllable process steps. 

Apart from characteristic material values such as the coefficient of linear thermal expansion, transformation temperature, and elastic properties, the cooling rate (Fig. 3.4-31) and the shape can also have a considerable 

SeaUng glasses may be classified by reference to the expansion coefficients of metals (e.g. tungsten and molybdenum) and alloys (Ni-Fe-Co, Ni-Fe-Cr, and other alloys) with which they are used. Hence sealing 

Tungsten 8486 Alkaline-earth borosilicate, high Lamp bulbs 

Metal a n/.fOO (lO-f /K) Glass number Glass characteristics Principal applications as scaling glass 

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The samples were collected and processed in a manner to avoid exposure to oxygen and control loss of moisture then they were pulverized to convenient sizes for research, ie, <149 fim ( — 100 mesh) and <840 fim (—20 mesh) the entire ton was thoroughly mixed and packaged in sealed glass ampules under nitrogen. These samples have been well characterized and are available in quantities that are expected to last for decades (Table 8). 

Butyryi chloride (butanoyl chloride) [141-75-3] M 106.6, f -89°, b 101-102°/atm, 1.026, Hp 1.412. Check IR to see if there is a significant peak at 3000-3500 cm (br) for OH. If OH is present then reflux with less than one mol equiv of SOCI2 for Ih and distil directly. The fraction boiling between 85-100° is then refractionated at atm pressure. Keep all apparatus free from moisture and store the product in sealed glass ampoules under N2. LACHRYMATORY - handle in a good fume hood. [Org Synth Coll Vol I 147 794/.]... 

Dissolve in Et20, add quinol (500mg for 300mL), dry over Na2S04, filter, evaporate and distil under dry N2. It is a clear liquid if dry and decompose very slowly. In the presence of H2O traces of tributyl tin hydroxide are formed in a few days. Store in sealed glass ampoules in small aliquots. It is estimated by reaction with aq NaOH when H2 is liberated. CARE stored samples may be under pressure due to liberated H2. [J Appl Chem 7 366 1957.]... 

Treatment of resin-bound iminophosphorane 197 with an excess of solid CO2 and CS2 in a sealed glass tube, and with aryl isocyanates afforded I-OXO-, 1-thioxo- 198, and l-arylimino-l//-pyrido[l,2-c]pyrimidine-3-car-boxylates 199 (OlJMClOll). Reaction of iminophosphorane 200, derived from 2-(2-azidophenyl)pyridine with excess PPh3, yielded 6//-pyrido[l,2-c] quinazoline-6-thione (201). 

Oxygen-sensitive substances. Substances that are moderately sensitive to oxygen (such as crystalline coelenterazine and Cypridina luciferin) can be stored aerobically at below — 70°C in a desiccated container for many years. They can be permanently stored in an evacuated fuse-sealed glass container even at room temperature, in darkness (for the technique, see Method II below). 

Fig. A.2. The sequence of making a sealed glass tube, from top to bottom.

To prepare CO solution for the experimental purpose, it is recommended to bubble 20 ml of stock solution in a sealed glass tube with a stream of pure CO gas. The bubbling process lasts for 20 min under the pressure of 100 kPa at 37°C [3]. One microliter of this CO-saturated solution is estimated to contain 30 ng of the gas based on the solubility of CO at 37°C, the extent of dilution of the CO-saturated solution, and the assumption that the loss of the added CO from the bath solution at the time of experiments is negligible. The stock solution of CO should be freshly prepared before each experiment and then should be diluted immediately to the desired concentration with the bath solution or culture media. 

Stability. It may be stored indefinitely at 0° in sealed glass ampules (Ref 20)... 

Explds at 60° after 13 sec in a sealed glass tube (Ref 4). Explds spontaneously when frozen and then thawed. Compd is a violent expl, extremely sensitive to impact or friction. It Jalso explds on exposure to strong light (sunlight or diffused), or when in contact with P, As, ozone, fused alkalies, and organic matter such as turpentine rubber, but not with sugar or resins. Metals strong acids do not cause it to expld,... 

On cooling (NH4)2S5 crystallizes as yellow to orange-yellow needles which melt at 95 °C in a sealed glass tube but decompose in air [reverse reaction at Eq. (17)] and on dissolution in water. (Et4N)2Ss is obtained by reaction of Et4NCl with Na2S5 in ethanol [33]. 

In carefully dried (vacuum-baked) and sealed glass containers gaseous S2O can be kept at 20 °C and partial pressures of below 1 mbar (100 Pa) for several days but at 180 °C the decomposition to SO2 and sulfur is complete within 1 min. At higher partial pressures gaseous S2O decomposes at 20 °C to SO2 and a yellow, relatively stable solid polymeric sulfuroxide of composition S>30 (see below). This decomposition is accelerated by traces of water and by irradiation with UV radiation [18]. 

Ring-opening polymerization was used to synthesize PTMC. The polymerization was carried out in evacuated and sealed glass ampoules with stannous octoate as a catalyst. The schematic reaction equations are shown in Schemes 8.7 and 8.8. The reaction time for aU homo- and copolymerizations were three days and the reaction temperature at 130 2°C. The obtained polymers were purified by dissolution in chloroform and precipitation in isopropanol. The precipitated polymers were collected, and washed with fresh isopropanol, and dried under reduced pressure at room temperamre until constant weight. 

Marty, C. and Berset, C., Degradation of rra - 3-carotene during heating in sealed glass tubes and extrusion cooking, J. Food ScL, 51, 698, 1986. 

Again we mention only a selection from the many sealing glasses which are made. 

When the multiple sheath is completed each cork is removed in turn and replaced by a beaded rod which is fused into place after careful scraping away of any burnt cork. The finished work should be well annealed. We find the method described here to be very serviceable and useful even when beads of a special sealing glass can be employed. 

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