388 PURPLE DYEING, ANCIENT AND MODERN. 



In Germany the manufacture of ultramarine proceeded at a far sloAVCr and 

 less profitable rate, though the directions published by Gmcliu would have 

 amply sufficed for manufacturing on a. much larger scale. He already kne^y 

 that the proportions of silicious earth, natron, and potter's clay might vary to a 

 certain extent without at all affecting the result; and he had also found that 

 the pr()duction of artificial ultramarine requires two distinct operations, viz: 



1. The production of the so-called green ultramarine; and, 



2. The transmutation of the green into thn blue article by roasting the former, 

 while allowing the access of air. 



This latter necessity he was taught by the accidental bursting of a crucible. 

 His observation of this accident enabled him to master the whole process, and 

 conduct it to any desirable issue. To the manufacture on an extensive scale, 

 however, the conditioTi insisted upon by Gmelia of perfect or chemical purity in 

 the silicious earth and the potte.'s clay employed, continued to present an 

 embarrassing obstacle on account of the delay and difficulty in bringing the 

 material to that state. 



It is true that he had himself raised the question whether the production of 

 the two expensive materials, both of them bchig components of potter's clay, 

 might not be dispensed with, and he experimenti'd upon various specimens of 

 tolerably pure clay containing the maximum of 4J per cent, of iron. But he 

 considered the results of the experiments unsatisfactory, on account of the 

 presence of even such a proportion of iron. From a porcelain clay containing 

 very little iron he obtained, indeed, a very beautiful ultramarine, which he con- 

 sidered quite fit for oil painting, especially for landscapes. But even this pro- 

 duct could by no means be compared to the natural and most beautiful kind. 

 The artificial article always retained a scarcely perceptible tinge of green and 

 gray; while the positive red, on which depends the peculiar brilliancy of the 

 natural ultramarine, was wanting. This difference was especially noticeable 

 when both pigments were rubbed in oil. The circumstance that Gmelin aspired 

 to the highest excellence, and would not content himself with mere mediocrity, 

 was aii obstacle to the introduction of this article into German industry, and 

 restricted its use when it was introduced. Still, the first German manui'actory 

 on the principle of Gmelin's process commenced working in 1S34, under the 

 management of Leverkus, of Wermelskirchen, and very soon occasioned a 

 great change alike in the price and the popularity of the article. 



In 1832, the celebrated French chemist, Dumas, in his "Manual of Chemis- 

 try," had expressed the opinion that chemical purity of materials might very 

 well be dispensed with in the manufacture of artificial ultramarine, and that 

 common clay might be used, provided it did not contain too much iron. Pro- 

 fessor Engelhardi, of the Polytechnic School, Nuremberg, while translating the 

 works of Dumas into German, was especially impressed by that statement, 

 and was induced thereby to make new experiments, but his labors were termi- 

 nated by death before he had obtained any positive and satisfactory results. 

 His assistant and successor, Leykauf, continued the deceased professor's experi- 

 ments, and was fortunate enough to succeed, where all previously had failed. 

 Bi^' means of potter's clay, Glauber's salt, and coal, he manufactured the most 

 beautiful ultramarine, in the renowned manufactuory of Ley Rauf, Heyne & Co., 

 at Nuremberg; and in a very few years the firm counted its wealth by millions. 

 Nowhere else has this branch of industry acqixired such an extension ; being 

 conspicuous even among the diversified activities of Nuremberg, and justifying, 

 tli:^refore, a brief description in this article. 



In the vicinity of the Nuremberg railroad depot, the , attention of the ob- 

 sorvant traveller is pretty sure to be attracted by a stately and spacious mass 

 of buildings of white and red sandstone. The long rows of structures, with 

 then- streets and yards, cover a space of some eighteen aci-es. Surrounded as the 



