US PATENT SUBCLASS 987 / 55
.~.~.~ At least one of the rings is devoid of N as ring atom (9/6558C)

Current as of: June, 1999
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987 /   HD   ORGANIC COMPOUNDS CONTAINING A Bi, Sb, As, OR P ATOM OR CONTAINING A METAL ATOM OF THE 6TH TO 8TH GROUP OF THE PERIODIC SYSTEM

30  DF  PHOSPHORUS COMPOUNDS (9/02; 9/06) {15}
49  DF  .~ Ring is devoid of a P or a metal atom and contains at least one hereto atom (O, S, N, Se, or Te) and may or may not contain C (9/547; 9/6524) {9}
54  DF  .~.~ At least two different rings containing hetero atoms or wherein, if the rings are the same, the substituents on at least two of the rings are different (9/6558; 9/6558B) {1}
55.~.~.~ At least one of the rings is devoid of N as ring atom (9/6558C)

DEFINITION

Classification: 987/55

At least one of the rings is devoid of N as ring atom (9/6558C):

(under subclass 54) Subject matter wherein the phosphorus compound contains at least one heterocyclic ring which is devoid of a nitrogen atom as a ring member.