Eutectic fusion

Early discussions, by Tammann and by Hedvall, considered the possible existence of a common characteristic (approximate) temperature for a solid at which chemical interactions with other reactants became detectable. For example [111], such a characteristic temperature for CaO, measured in various reactions with CuS04, Co3(P04)2, MgC03, and MnSi03, was found to be 788—838 K. Similarly, the onset of reaction of BaO with the sulphates of Mg, Ca, Sr, Co, Cu, and Zn occurred between 601 and 645 K. In the latter example, it has been shown that the fusion of Ba(OH)2 (an impurity not easily excluded from BaO) could contribute to the initiation of reaction. Eutectic formation during the reactions of BaCl2 with alkali metal sulphates... 

Fusion welding is possible because copper, a component of most gold and silver alloys, easily forms eutectics, alloys that melt at a temperature lower than any of the metals composing them (Duval et al. 1989 Wolters 1983, 1981). To attach granules or wires to a surface of gold or silver alloy... 

Protection of the molten metals from air and moisture The protection of the molten metals has always been an essential point. Fusion under vacuum or an inert atmosphere (pure He or Ar, possibly gettered) is systematically used. In the past, also for small scale laboratory preparations, fusion under a protective layer of molten non-reactive salts was often used. Low density salt mixtures having low-melting point and high-boiling point were generally employed (for instance eutectic mixtures of anhydrous stable alkali halides). 

The melting points of pure naphthalene and pure benzene are 80.2°C and 5.4°C, respectively. The average enthalpies of fusion of naphthalene and benzene in the temperature range are 10,040 and 19,200 J mol, respectively. Calculate the temperature and composition for the maphthalene-benzene system that correspond to point B, the eutectic point, in Figure 14.3. 

In addition to Eqs. (126) and (127), the other necessary thermodynamic properties of HgTe(s) and CdTe(s) are given in Table VII. The enthalpy of fusion for CdTe(s) is based upon a single determination by Kulwicki (1963). The -rich eutectics listed are from Kulwicki for CdTe and from Strauss (1967) for HgTe. 

B. Karandeeff found that the fusion curves of the system KF—K2S04 gave eutectics at 883° (41 mols. per cent, of potassium fluoride), and 788° (83 mols. per... 

According to F. A. Fliickiger, lithium forms a basic carbonate lithium oxycar-bonate is a crystalline compound of lithium oxide and carbonate whose composition and limits of existence have not been explored. According to H. Ie Chatelier, the fusion curve of mixtures of potassium and lithium carbonates shows two eutectics, one at 5C0° and the other at 492°, corresponding respectively with 26 and 46 6 per cent, of lithium carbonate. The intermediate maximum at 515° corresponds with the formation of the double salt, lithium potassium carbonate, LiKC03. 

E. Mitscherlich 20 found that an intimate mixture of potassium and sodium carbonates fuses at a lower temp, than either salt alone, and E. Stolba found that at ordinary temp, the sp1 gr. of the fused mass was 2 53-2 56. H. le Chatelier obtained the V-eutectic at 6 J0° with 48 5 per cent. Na2C03 with no sign of the formation of a compound of the two salts at fusion temp. These facts of course do not prove the formation of a chemical... 

YaJ. Lehman, A Method for the Analysis of Technical Trinitroxylene (Xylyl) , Trudy LKKhTi, No7, 127-41 (1939) Khim Referat Zhur 2 (5), 66-7 (1939) CA34,2604 (1940) [To ascertain the individual percentages of trinitro-m-xylene and trinitro-p-xylene in a mixt contg these two compds, the temp at the start of crystn of the mixt and the eutectic temp of the mixt are measured. The individual % of each compd can then be detd from a binary fusion diagram of these compds]... 

Ammonium nitrate is also miscible with fused salts of nitric acid. The composition of the eutectics and the fusion temperatures of mixtures with sodium, potassium, and calcium nitrate are considered in future chapters (Vol. III). Data concerning the properties of mixtures with guanidine nitrate, nitroguanidine, ethylene diamine dinitrate, are also reported in Vol. III. 

Le Roux [64] reports that ethylenediamine dinitrate forms an eutectic with ammonium nitrate 50/50, the fusion temperatureof which is above 100°C. He suggested using a mixture composed of 50% of ammonium nitrate and 50% of ethylenediamine dinitrate instead of amatol 50/50. 

The fusion curve of mixtures of arsenic and iodine shows no evidence of the formation of a pentiodide, but there is a eutectic, of freezing point 71-5° C., which has the approximate composition of this substance.5 The absorption spectrum of the solution in carbon disulphide is similar to that of a mixture of the triiodide and iodine.3... 

CRYOHYDRATE. An eutectic system consisting of a salt and water, having a concentration at which complete fusion or solidification occurs al a definite temperature (eutectic temperature) as if only one substance were present. 

According to R. Boulouch, the f.p. curve of varying proportions of phosphorus and sulphur associated by fusion at temp, below 100° consists of two lines, Fig. 51, which cut sharply at the eutectic temp., 9-8° and 22-8 per cent, of sulphur. Hence, there is no evidence of the formation of a definite compound of the two elements below 100°. Mixed crystals, or solid soln., rich in sulphur are formed, and these are isomorphous with octohedral sulphur similarly, mixed crystals, or solid soln., rich in phosphorus, are isomorphous with phosphorus. F. Isambert found that when a mixture of phosphorus, even with a large excess of sulphur, is distilled at 100° in vacuo, all the phosphorus distils over, and a residue of sulphur remains. H. Giran heated mixtures of the two elements in sealed tubes at about 200°, and... 

As with the chlorometallate eutectics a model for the effect of HBD on the freezing point depression of the mixture would be beneficial for the design of new liquids. No correlations were observed between the freezing point of the mixtures and the enthalpy of formation or fusion of the pure acids but Table 2.5 shows qualitatively that the larger depressions of freezing point occur with the lower molecular weight HBDs. 

A second interpretation is that the liquid phase previously formed between dolomite and soda ash was required for the reaction endotherm peak at 706°C, implying a fusion reaction rather than eutectic melting amongst solids. This is refuted by evidence discussed subsequently where the disappearance of this endotherm with decreasing particle size (increasing volume of liquid phase) implies that interparticle contact was required for this reaction. 

The endotherm which peaked at 816°C has no corresponding endotherm in any of the chosen binary systems. However, this endotherm was clearly apparent in the ternary mixture, silica-soda ash-calcite, implying liquid formation amongst these three constituents. This fusion process was not eutectic, since an active participant in this reaction is expected to have been the... 

The endotherm that peaked at 706°C was correlated to eutectic melting between CaCOj, Na2C03, and MgO. It could also be interpreted as a fusion reaction involving these phases and pre-existing liquid phase. This endotherm appears in the 90-125 /xm and 63-90 /xm particle size mixtures as well, albeit more diffusely, but does not appear in DTA traces for the two finest particle size mixtures. It is interpreted that for the 45-63 /xm particle size and smaller, an adequate quantity of liquid phase was formed (associated with the peak at 651°C) to have prevented the solid particle contact necessary for CaCC>3-Na2C03-Mg0 eutectic melting. This further implies that preexisting liquid phase was not a participant in this reaction. 

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