CHEMICAL SCIENCE. 185 



of a line could be detected. After thirty-six hours' treatment with 

 ozone, the coloring matter was entirely destroyed, and the most care- 

 ful scrutiny of the page would have failed to discover that any of the 

 lines had once been painted over. In like manner, a wood-cut of 

 Durer, which had been besmeared with a dark yellow color, was 

 completely restored. 



Writing ink may be readily discharged by ozone, especially if the 

 paper be subsequently treated with very dilute chlorhydric acid to 

 remove the oxide of iron. 



Printer's ink is not attacked by ozone, to any appreciable extent, 

 unless the action be long-continued. Vegetable coloring matters are 

 completely removed by it, but metallic coloring matters, grease spots, 

 and stains produced by fungi, cannot be destroyed. 



As applied in the small way, the method consists in placing a bit 

 of phosphorus, about three inches in length, and half an inch in 

 diameter, the surface of which has been scraped bright, in a wide- 

 necked glass carboy, or other large hollow vessel, pouring in as much 

 water, at about 30 Cent., as will half cover the phosphorus, closing 

 the vessel with a cork, and allowing the whole to stand until the jar 

 is charged as strongly as possible with ozone, which ordinarily occurs 

 after twelve or eighteen hours. Then, without removing the phos- 

 phorus or water, the paper to be bleached, which has been moistened 

 with water, rolled up, and fastened to a platinum wire in a suitable 

 manner, is hung in the middle of the vessel. The cork is now restored 

 and the apparatus left to itself. The roll of paper is soon surrounded 

 with the fumes arising from the phosphorus, and the stains gradually 

 disappear. The rapidity of the operation, of course, depends upon 

 the nature of the substance to be discharged, three days having 

 been the longest time required in any of the experiments. Prints, 

 which had merely become brown by age, and those stained with 

 coffee, usually become perfectly white and clean in the course of 

 forty-eight hours. The action of the ozone, however, must not be 

 continued too long, lest some of the finer lines of the engraving should 

 be injured. After all the spots have disappeared, the paper is strongly 

 acid, and if allowed to dry when in this condition would become 

 exceedingly brittle and also dark-colored. It is consequently neces- 

 sary to remove the acid completely. In order to accomplish this, the 

 paper is placed in water, which is frequently renewed, and allowed to 

 lie there until a lot of blue litmus paper, pressed against it, is no 

 longer reddened. The paper is then passed through water to which 

 a few drops of a solution of soda have been added, and is spread upon 

 a glass plate ; this is slightly inclined, and a fine stream of water is 

 allowed to flow over the paper during twenty-four hours. After the 

 paper, on exposure to the air, has become dry enough to remove from 

 the glass without danger of tearing, it is taken off and pressed dry 

 between folds of filter-paper. The author remarks that, in case the 

 process were attempted on a larger scale, it would probably be well 

 to have glass troughs or boxes blown, of the desired form, since it is 

 not easy to prepare suitable vessels by any process of fastening to- 

 gether pieces of glass, the cement being attakced by ozone. 



Attempts to apply ozone in restoring oil paintings gave only nega- 

 tive results, the action having been irregular, 

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