Congruent compounds

In the case of TiC, preferential evaporation of titanium leads to a change in the stoichiometry of the compound towards the carbon-rich end, the excess carbon being left diffuses into the carbide phase, and so the flux ratio of the two elements changes widi time until congruent vaporization is achieved. 

Addition of the appropriate amount of water to anhydrous H3PO4, or crystallization from a concentrated aqueous solution of syrupy phosphoric acid, yields the hemihydrale 2H3PO4.H2O as a congruently melting compound (mp 29.3 "). The crystal structure shows the presence of 2 similar H3P()4 molecules which, together with the H2O molecule, are linked into... 

J. B. Ott and J. R. Goates. "Summary of Melting and Transition Temperatures of Pure Substances and Congruent and Incongruent Melting Temperatures of Molecular Addition Compounds," J. Chem. Eng. Data. 41. 669-677 (1996). 

Safonov et al. 330) also investigated the In-Te-I system by DTA and X-ray diffraction. The system contains three, congruently melting, ternary compounds InTel, Inl3-2Tel4 and InIs-STel, of which the latter two are out of the scope of this review. InTel melts congruently at 475°C. It forms part of the quasibinary cuts In Tea-Inla and Inl-Te, where the sections InTel-In Tes, InTel-Inia, InTel-Ini, and InTel-Te are all of the eutectic type (80). 

Dissolution of CaCOs is a congruent reaction the entire mineral is weathered and results completely in soluble products. The above reaction is driven to the right by an increase of CO2 partial pressure and by the removal of the Ca and/or bicarbonate. Any impurities present in the calcareous rock, such as silicates, oxides, organic compounds, and others, are left as residue. As the calcium and bicarbonate leach... 

The Ca-Cu system has been reexamined using thermal analysis and x-ray diffraction methods an independent study of the CaCuj-Cu section has also been completed. The resultant phase diagram, although similar to that in ref. 3 at the Cu-rich end, differs markedly for Ca-rich alloys. Supporting evidence for the modifications has been obtained from the Ca-Mg-Cu ternaiy system. Three intermediate compounds are formed in the system CaCuj (950 C) melts congruently, whereas CajCu (488 C) and CaCu (567°C) are formed in peritectic reactions. Single-crystal x-ray diffraction studies verify the stoichiometry of CajCu and examine the polymorphism of CaCu. ... 

The entire Ba-Cu system has been examined a partial study (0-50 at% Ba) has also been carried out. Where comparable the two sets of data are in agreement consequently, the recommended phase diagram is that in ref. 1. Two compounds exist in the system BaCu (570°C) melts congruently, whereas BaCujj (670°C) is formed in a peritectic reaction. Further evidence for BaCu has come from a structural study. ... 

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