Germanate Melts

Germania melts are quite strong liquids, with viscosities between those of silica and boric oxide. Addition of very small quantities of alkali oxides to germania results in a sharp decrease in viscosity, with a 

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The overall glass composition is by far the most important factor in controlling the batch-free time. Simple oxide mixtures, such as those used to produce calcium aluminate glasses, often form eutectic mixtures which melt directly with very short batch-free times. Many non-silicate melts are very fluid at any temperature above the melting point of their components and rapidly dissolve all batch particles. Borate, phosphate, and germanate melts can be formed at much lower temperatures than are typically required for silicate melts. As a result, it is usually easier to decrease their viscosity by increases in temperature, e.g., an increase in temperature from 1000 to 1200 C is more easily attained than an increase from 1400 to 1600 C. 

Figure 6.7 Effect of composition on the 10" Pa s isokom temperature for sodium germanate melts...

Figure 11.3. Effect of composition on the diffusivity of water at 1100 °C in sodium sili cate and germanate melts (Germanate data supplied by M. Hall)...

Operating parameters of this German plant, on the basis of one cubic meter of raw gas, iaclude 0.139 m O2, 0.9 kg briquettes, 1.15 kg steam, 1.10 kg feed water, 0.016 kWh, and 1.30 kg gas Hquor produced. Gasifier output is 1850 m /h and gas yield is 1465 m /t dry, ash-free coal. The coal briquettes have a 19% moisture content, 7.8% ash content (dry basis), and ash melting poiat of 1270°C. Thermal efficiency of the gas production process is about 60%, limited by the quaHty and ash melting characteristics of the coal. Overall efficiency from raw coal to finished products is less than 50%. 

Georgius Agricola, a German scientist of the sixteenth century, was the first to mention bismuth detailing the melting of bismuth from ore (1). It was ia the sixteenth century that bismuth compounds were first discovered to have a soothing effect on stomach disorders. Bismuth compounds are stiU widely used ia preparations to reheve this condition. Not until the 1800s was bismuth refined and proven to be an element. Until that time, bismuth was usually referred to as one of the other elements with which it is associated ia ores such as antimony, silver, lead, and tin. 

Orotic acid (971) has a chequered history. It was isolated in 1905 from the whey of cows milk in Italy and it was subsequently synthesized in the United States in 1907. However, the workers involved were discouraged by some difference in melting points and no direct comparison of specimens was ever made. To make matters worse, the same laboratories prepared the isomeric 5-hydroxy-2-oxo-l,2-dihydropyrimidine-4-carboxylic acid and announced it as orotic acid, again without any direct comparison. Only in 1930 did a German worker actually compare directly natural and the original synthetic orotic acid, thereby showing them to be identical (30CB1000). 

In addition several other materials have been reported by industrial companies, but have not at the time of writing been commercialised. These include the product of condensation of 2,2-bis-(p-aminocyclohexyl)propane (VI) (Figure 18.28) with a mixture of adipic and azelaic acid (Phillips Petroleum), a research material produced in the old German Democratic Republic obtained by melt condensation of /ranj -cyclohexane-l,4-dicarboxylic acid (VII) (Figure 18.28) and the two trimethylhexamethylenediamine isomers used in the manufacture of Trogamid T, and another amorphous material (Rilsan N by Ato Chimie). 

The sevenfold activity against houseflies credited to DFDT by the Germans actually represents the comparative activity of Gix, the active constituent of which is DFDT. It is possible that the other constituents of Gix acted as a synergist for the DFDT. Alessan-drini (2) reports the isolation from Gix of a compound melting at 99° to 100° C., which obviously is not DFDT. A crude sample of DFDT, a sample of recrystallized DFDT, and a sample of the impurities separated in the recrystallization of DFDT were found by Fay... 

Name from tung sten (Swedish = heavy stone) chemical symbol wolfram derived from Wolfrahm (Middle High German) like a wolf, it stole the desired tin in melting furnace... 

In a second Walden cycle, germane S -3 was converted to the chloro derivative R-13, which was reduced by LiAlPLt to the enantiomeric germane R-32. The configuration of the chloride J -13 was assigned by mixture melting point with the known R sila analogue and from consideration of Brewster s rales. Thus, chlorination must proceed with retention and hydride reduction with inversion of configuration. 

We understand now why fluorescence contains the term fluor, but what is the origin of fluorspar or fluorspath and why are these materials fluorescent Spar (in English) and spath (in German) were the names given in the eighteenth century8 to stones that are more or less transparent and crystallized with a lamellar texture. Because these materials can be easily melted, and some of them can help to melt... 

Thiele, U., Which criteria of polymer lines of PET Production determine quality and purity of the melt (in German), presentation given at the 3rd Plastic Symposium ofGneufi Bad Oeynhausen, Germany, 15-16 September, 1999. 

At temperatures germane to melting and erystallizrng mantle magmas, Li isotopes do not show permil-level mass fractionation (Fig. 4 Tomascak et al. 1999b). This has since been corroborated by examination of bulk rocks and olivine separates from basaltic lavas, which yield consonant isotopic values (Chan and Frey 2003). Also, whole rocks and omphacite mineral separates from alpine eclogite with metamorphic peak temperatures approximately 650°C (Zack et al. 2003) show no consistent Li isotopic difference. 

However, changes in the seasonality of snowmelt coupled with shifts in precipitation patterns may result in water shortages in the summer and autumn, especially in downstream regions. For the River Rhine, for instance, some scenarios show a decrease in total discharge of more than 50% at the German-Dutch border for the low-flow period in the autumn [78]. Moreover, the declining impact of snow and ice melt will increase the year-to-year variability of discharge in the summer and autumn. 

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