PUKPLE DYEING, ANCIENT AND MODERN. 393 



from the most skilful and laborious analysis, wliicli is the essential product 

 and which the accidental ? Which the portion which conduces to the pro- 

 duction of the color, and Avhich the portion that, to a greater or less extent, 

 limits its quantity and diminishes its brilliancy ? The time spent in analyses, 

 thus inevitably indecisive, may be considered as completely thrown away. In 

 truth, those analyses have rather raised questions than settled them. The in- 

 fluence of iron, for instance, upon the production and the color, which long ago 

 was considered a settled tact, is now relegated into the realm of doubt. There 

 seems good reason to believe that sulphur has a chief, if not the sole, part in 

 coloring the green and blue ultramarine ; but how — through what combinations ? 

 The material itself opposes difficulties to our clear view of the subject ; and the 

 difficulties arc increased by the coincidence of two chemical processes, and by 

 the facile decomposition of the material the moment it is attacked by reagents. 

 Finally, we are but too imperfectly acquainted with the affinities of sulphur 

 and the recently discovered sulphuric acids for the alkalies. This power- 

 lessness of analysis to pronounce definite judgment has necessarily given 

 rise to various opinions, founded not upon facts, but upon fancies, and, a3 

 usual in such cases, the opinion founded upon f\incy has been more per- 

 emptorily asserted than the knowledge founded upon fact. Of the green ultra- 

 marine, we have seen it positively asserted, though without even an attempt at 

 proof, that it is a simple combination of sulphur natrium, while another disputant 

 is not less positive that it is a mixtuie of blue ultramarine with some yellow 

 substance, the elimination of which turns the green to blue. Others assert that 

 the acid has transformed the sulphur natrium of the green ultramarine into a 

 sulphuric metal, combined with other and unascertained matter; that oxydi- 

 zation has taken place, and the sulphur has united with the undocomposed 

 sulphuric natrium. According to others the oxygen acts upon the sulphur and 

 forms a sub-sulphuric acid, or some other of the recently dit^covcred sulphuric 

 acids. In short there has been much disputation, but no approach to a conclu- 

 sion which can be relied upon. To arrive at such a conclusion we must, as 

 our starting point, first study the affinities of aluminum and sulphuric natrium. 



All that we are thus far warranted in saying is simply this, that ultramarine 

 contains silicious earth, potter's clay, natron, and sulphur. But, what else ] 

 That is the real question at issue. The silicious earth is, if not superfluous, at 

 least inoperative, as regards the production of the blue color ; but, though not 

 itself the cause of the blue color, it at least supplies the fire-proof quality. Too 

 much of it, undoubtedly, is injurious to the color. If the silicious acid be not 

 fixed by natron, the blue color is either very much faded, or wholly destroyed, 

 and the ultramarine is rendered unfit for the purposes of the porcelain painter. 

 The artificial ultramarine has still another great advantage over the natural. 

 While the latter could only be used for oil paintings, the former can be used in 

 every art in which the blue color is indispensable, and consequently it has, to 

 a very considerable extent, supplanted cobalt, litmus, and Prussian blue. 

 Even when the ultramarine commanded a far higher price than smalt, (the lat- 

 ter selling, in France, at 47 to 50 cents per pound, while the former could not 

 be purchased for less than from $1 62 to %\ 73,) it was found that ultramarine 

 was the cheaper article, for the simple reason that one pound of ultramarine 

 Avould do the work of ten pounds of cobalt blue. 



Ultramarine is a reliable color for oil painting or for painting on glass, for 

 tapestry, and for paper-hangings in patterns, and for the coloring of soaps, 

 candles, &c., &c., and it is not easy to over-estimate its importance in printing 

 on wool, cotton, linen, or silk. To the French manufacturer, Blondin, belongs 

 the credit of having been the first to use ultramarine in cotton printing. For 

 six years he kept his application a secret ; but, in 1S44, Dolfus, a cotton manu- 

 facturer from Alsace, visited the French exhibition and made himself master of 

 the process. Since tlleu, as is said in the report of the French exhibition of 



