LO-KAO.

43i

The following is the descripition of the process as carried out at A-ze, andwitnessed by Helot:—The fresh (green) bark of the hong-pi-lo-chou is firstboiled with water, and left standing in that liquid for two days ; the preparationof the infusion of the green bark of the pe-pi-lo-chou lasts for ten days. Eachof these infusions is separately employed, and when used lime-water is added.The cloth is first dipped from seven to ten times in the hong-pi bath, and nextthree times in the pe-pi bath, but the fabric is dried after each separate im-mersion. This drying is effedted in meadows, where the cloth is spread outat about nightfall, and left until noon the next day, the adtion of the sunbeing indispensable for the development of the colour, only the side of thecloth exposed to the sun’s rays being dyed. It is a remarkable fadt that thisChinese cloth thus green-dyed is very intensely coloured on one side, andonly faintly so on the other. This appearance induced Persoz to doubt thecorredtness of Helot’s statement, Persoz expressing himself on this matteras follows :—Since the Chinese green-dyed fabrics have a right and wrong side,they cannot have been dyed by immersion, but the dye has evidently been im-parted to the cloth either by a brush or other mechanical means; while,moreover, the change which the colour undergoes by exposure to the sun’srays proves that the dye has not been imparted in the way described byHelot.

The researches, however, of M. Michel on indigenous European plants ofthe same genus as those used in China clear up this subjedt, as we shall seepresently. The cloth dyed as above described, having become quite dry, isplaced in cold water, and thoroughly washed and rinsed through ; the wash-waters are colledted together, poured in a large cauldron, and the water is boiledafter there has first spread over its surface a tight network of cotton yarn,upon which the colouring matter is deposited during the process of ebullition.In order to colledt a quantity of the colouring matter, this process of ebullitionhas to be repeated with fresh quantities of water wherein the previously dyedcloth has been washed. When the cotton yarn is sufficiently charged withpigment the former is washed in cold water, and well rubbed with the hands,by which means the lo-kao becomes detached, and slowly settles in the water;the precipitate is washed by decantation, and the thin pasty mass of pigmentis placed upon paper, and dried by first absorbing a portion of the moistureby means of ashes, and next dried in the sun. The layer of lo-kao whiledrying becomes detached from the paper, and by the latter being bent the pig-ment presents the aspedt of the irregularly shaped, small, thin, yet hardlaminze as met with in commerce. The weight of cotton yarn required toexhaust the pigment from 300 pieces of dyed cloth, the length of these piecesnot being mentioned, is 3-62 kilos. In order to obtain the weight of 1 kilo, oflo-kao, 1060 pieces of dyed cloth are required, and since, according to thestatements of Helot, the five manufactories of lo-kao at A-ze cannot annuallyyield more than from 18 to 24 kilos, of lo-kao, the high price of that substanceis readily explained.

M. Michel, at Lyons, has experimented with the bark of the Rhamnuscatharticus, following the same mode of operation as that described,—that isto say, placing cloth in aqueous infusions of the bark, and repeating thesedippings, each being followed by a drying of the cloth by exposure upon grassduring the night and a portion of the daytime : he obtained a rather intensely