| 556 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES | 
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| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {3} | 
| 1 | DF | .~ HEAVY METAL CONTAINING (e.g., Ga, In or T1, etc.) {19} | 
| 64 | DF | .~.~ Arsenic, antimony, or bismuth containing (As, Sb, or Bi) {5} | 
| 70 | DF | .~.~.~ Carbon bonded directly to the metal {1} | 
| 71 | DF | .~.~.~.~ Chalcogen bonded directly to the metal (e.g., arsine oxides, etc.) {1} | 
| 72 |  | .~.~.~.~.~ Plural chalcogens bonded directly to the metal {1} | 
| 73 | DF | .~.~.~.~.~.~> Exactly three chalcogens bonded directly to the metal (e.g., arsonic acids, arsonates, etc.) {1} |