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Syn. Gen-seï, Seki-seï, Tai-seï, and is used in Chinese medicine as a caustic against some diseases of the eye and malignant ulcers. But the chief use is as a drawing and painting material.
It should be observed that the name Kon-jo is a common name used by the common people for the most different blue dyes, and principally for the Japanese indigo (Dye of Polygonum tinctorium Lour.) This latter substance has, however, its own proper name, namely, Rai-den or Ai-no-ori. True Kon-jo is blue copper-malachite.
A sandy variety of this ore is found also in Japan and is called Heng-sei or Suna-konjo. It should be known that, after the introduction in Japan of European Ultramarine, the name Suna-konjo is also given by Japanese drug-merchants to this latter substance. Real Suna-konjo is mountain-blue.
Seventh,—Blue Vitriol, Blue Stone (sulphate of copper) is found in several Japanese coppermines either as an earthy aggregate, or in solution as “blue water,” both being disintegrating products of copper-pyrites formed by a long continued action of air and water. The Japanese also know how to prepare this salt by roasting copper-pyrites with free access of air and treating the roasted mass with water. This salt is, however, very impure. It can be found in every drug-shop under the name of Tan-pan or Seki-tan, Syn. Sei-seki-shi, Ao-ishi-no-ko. Since the earliest times it has been used in Chinese medicine as a caustic in eye-disease, blennorrhœa and bites of snakes and other animals. Its conserving properties for wood are also known to the Chinese and Japanese. Tan-pan is prepared either out of the mineral, or by evaporation of the “blue water” in Akita province of Dewa; Tokoro-no-kuchi in Noto; Satsuma; Ashiwo-yama in Kotsuke and many other places.
The preparation of cement copper out of the “blue water” by means of precipitation with iron or zinc, seems to be unknown to the Japanese.
Eighth.—Metallic, dendritical copper (copper mass) seems to be rare in Japan, according to Burger l. c.
