Peritrichous crystal - Hosho

Also known as peritectic crystals. When crystals of one of the components coexist in a two-component liquid, the liquid reacts with the crystal to form a different crystal that encases the original crystal of one of the components. For example, if the concentration of salt in a salt and water system is constant, when the temperature is lowered to a certain level, the solution and crystals react around the salt (NaCl) crystals that precipitated at a constant temperature, forming NaCl･ _2H2O crystals, forming a peritectic crystal that encases the NaCl crystal. This reaction is called a peritectic reaction, and the temperature at which it occurs is called the peritectic point. The same thing often happens with binary alloys.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

包析晶ともいう．2成分からなる液体のなかに一方の成分の結晶が共存している場合に，液体がこの結晶と反応して別の結晶をつくり，もとの1成分の結晶を包み込んだ状態の結晶をいう．たとえば，食塩と水の系で食塩の濃度が一定の場合，ある温度まで下げると，温度一定のまま析出した食塩(NaCl)の結晶のまわりで，溶液と結晶が反応してNaCl･2H₂Oの結晶ができ，NaClの結晶を包み込んだ包晶ができる．この反応を包晶反応といい，このときの温度を包晶点という．2元合金の場合もしばしば同様のことが起こる．

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