. The book of photography; practical, theoretical and applied. this is so. Isomeric Di-substitutiox Products. Replacing two hydrogen atoms by hydroxyl!groups, it will be seen that three differentcompounds should be possible. OH OH I i c ,c HC C-OH H-C CH HC CHH (1) HC C- OHH \- (2) OH C H-C CH ! - ;lHC CH \-^ i OH (3) In (1) the two OH groups are next to oneanother; in C2) one CH comes between them,and in (3) two OH groups. Actually, threecompounds are known, having different chemi-cal and physical properties, yet all having themolecular formula CeH4(0H)2. These threesubstances are pyrocatecho
. The book of photography; practical, theoretical and applied. this is so. Isomeric Di-substitutiox Products. Replacing two hydrogen atoms by hydroxyl!groups, it will be seen that three differentcompounds should be possible. OH OH I i c ,c HC C-OH H-C CH HC CHH (1) HC C- OHH \- (2) OH C H-C CH ! - ;lHC CH \-^ i OH (3) In (1) the two OH groups are next to oneanother; in C2) one CH comes between them,and in (3) two OH groups. Actually, threecompounds are known, having different chemi-cal and physical properties, yet all having themolecular formula CeH4(0H)2. These threesubstances are pyrocatechol, resorcinol, andhydroquinone. In order to distinguish betweenthree isomeric di-hydroxy-benzenes they havereceived special names. Formula (1) is termedthe ortho, (2) the ineta, and (3) the^xira deriva-tive. OH I A HC C- OH I II HC CH ^ / C H Oitlio-di-liydroxy-benzene. Pyrocatechol. OH I A HC CH I IIHC C-OH C I H Meta-di-hydroxy-benzenc. Resorcinol. OH A HC CH I IIHC CH \ IOH Para-di-hydroxy-benzene. Hydroquinone. All these compounds can act as photographic. PRINT FROM BLUE BLOCK ONLY. mh
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