Abstract: A general-purpose organic rust inhibitor which can effectively prevent corrosion of metals, and which comprising a compound represented by the general formula (1): ##STR1## wherein, in the above general formula (1), R.sub.1 represents a fluorine-substituted alkyl group; R.sub.2 is a hydrogen atom or a group defined for R.sub.1 or an organic residue; R.sub.3 and R.sub.4 are hydrogen or an ionizable group at least for either of the two, or an ionizable group in which R.sub.3 and R.sub.4 are connected to each other.

Abstract: A general-purpose organic rust initiator which can effectively prevent corrosion of metals comprising a compound of formula (1): ##STR1## wherein R.sub.1 is a perfluoroalkyl group having 1 to 6 carbon atoms; R.sub.2 is a hydrogen atom or a group defined for R.sub.1 ; R.sub.4 is an acid group selected from --OH, --COOH, --SH, --SO.sub.2 OH, --PO(OH).sub.2, --SCH.sub.2 COOH, --SO.sub.2 NHCH.sub.2 COOH or a salt thereof; R.sub.3 is a hydrogen atom or a group defined for R.sub.4 ; or R.sub.3 and R.sub.4 together form an acid group selected from --N.dbd.N--NH--, --CH.dbd.N--N--, --SO.sub.2 --NH--CO--, --S--C(SH).dbd.N-- or a salt thereof.

Abstract: An endless inked ribbhon provided in a case is twisted in the form of a Mobius band. An inverting device is provided in the case for inverting the inked ribbon, and a reinking device is provided adjacent the inverting device for supplying ink to a lower half portion of the ribbon. The upper half portion of the ribbon, which has been supplied with the ink during the preceding cycle of the operation of the ribbon, is used for printing dots on paper.