Tantalum dust deflagration in a bag filter dust-collecting device.

An accidental tantalum powder deflagration with casualties occurred during the operation of a bag filter dust-collecting device. To understand the mechanism of the incident and its material hazards, experiments for determining the combustibility and ignition characteristics of the tantalum powder were performed. The magnitude of the tantalum dust explosion is classified as severe (K(st)=273), contrary to the classification found in the preceding literature. The minimum ignition energies for both a dust cloud and a dust layer of the tantalum powder were also found to be far lower than previous values. Judging from the observation of the surface with an SEM, the coral-like structure of each particle of the tantalum powder can enhance its fire and explosion hazards and affect its sensitivity to electrostatic sparks by increasing in particle surface area. A thin, non-conductive oxide layer of the tantalum powder surface has a high resistivity and generates electrostatic charge when rubbed with conductive materials like the wall of the collecting device. The authors conclude that the possible cause of the ignition was electrostatic discharge resulting from charging electrostatically.

[Clinical effects of NK 631, a new bleomycin derivative, in treatment of oral cancer (author's transl)].

We used only NK 631, a new bleomycin derivative, for 10 cases of primary oral cancer, and obtained following results. (1) Anti-cancer effects were immediate and as follow: remarkably good in 1 case, efficacious in 8 cases, and none in 1 case. (2) In clinical examination, peripheral blood, function of kidney, liver, etc. were normal. But attention must be payed to blood gas. (3) Loss of hair, stomatitis and exanthema were noticed as side effects more clearly than regular bleomycin, but no fever. As the result of the above, NK 631 is better than regular bleomycin in anti-cancer effect and activity, but more attention should be payed to the side effect.