CHEMICAL SCIENCE. 2GO 



means of a brush. He had observed that the action exerted by carbonate of 

 lime upon the silicates of potash and soda, viz., the displacement of silica, 

 was likewise exerted by the carbonates of baryta, strontia, magnesia, iron, 

 lead, etc., and even by other salts, such as chromate of lead, most of the 

 metallic carbonates, and even the oxides of lead and oxide of zinc. 



He endeavored at first to replace, in the application of mineral colors upon 

 stone, the fixed and essential oils usually employed by solutions of silicate 

 of potash. With white-lead, the formation of silicate of lead was too rapid 

 to permit the application of this color by means of the painting-brush. 

 Oxide of zinc gave satisfactory results. The artificial sulphate of baryta, 

 which had already found employment in whitening stones of too dark a 

 color, was again usefully employed; and, by mixing it in large proportion 

 with the oxide of zinc, Mr. Kiihlmann obtained a white color of greater 

 brilliancy and transparency. It appeared, at first, that sulphate of baryta 

 could not be employed by itself; but it was found that by applying it 

 repeatedly, by means of glue or starch-paste, or by means of a mixture of 

 starch-paste and silicious solution, it covered as well as white of lead and 

 zinc-white in painting with size or paste colors. This observation was of the 

 highest importance; a new white color was found which could be employed 

 in the place of those hitherto in use. 



New While Color (Base Blanche). Your commission has been vividly 

 impressed with the results already obtained by the employment of artificial 

 sulphate of baryta in the decoration of several buildings at Lille. The bril- 

 liancy and whiteness of the finest white-lead is but dim when compared 

 with painting in sulphate of baryta. This color possesses the advantage of 

 remaining unaltered under the influence of emanations of sulphuretted 

 hydrogen; it enables us to execute dim or lustrous white paintings at a 

 saving of about two-thirds. Its use must likewise appear of immense 

 service viewed from a sanitary point of view. It gets rid, on the one hand, 

 of the dangers attending the manufacture and application of white-lead and 

 oxide of zinc; on the other, of the odor of the essential oils. Mr. Kiihlmann 

 has not shrunk from establishing the manufacture of this baryta-white upon 

 a large scale. In his works at Loos, the native sulphate of baryta or heavy 

 spar is transformed into chloride of barium, which, when treated in its turn 

 wilh sulphuric acid, at the works of St. Andre, is again converted into 

 sulphate of baryta, which is thus obtained in a state of extreme division 

 and purity. 



Mr. Kiihlmann, passing from whites to the various colored mineral sub- 

 stances, has observed that, under the influence of silicate of potash or soda, 

 the same reactions are produced; that colors which are alterable by the 

 alkalies cannot be employed, but that the ochres ma}' be used, as well as 

 blue and green ultramarine, oxide of chromium, zinc-yellow, sulphide of cad- 

 mium, red-lead, calcined lamp-black, oxide of manganese, etc.; that the 

 colors Avhich dry slowty may be rendered fit for painting by mixing them 

 with colors which dry more readily, or by the addition of white colors which 

 dry rapidly. He found, moreover, that colors which were ground with a 

 concentrated solution of an alkaline silicate may be applied more readily 

 upon silicified stones than upon those which have not been silicified; that 

 in this latter case it is always useful to impregnate the surfaces, some little 

 time before applying the colors, with a weak solution of silicate; that, in 

 painting apartments, the ordinary process of painting in distemper will be 

 found sufficient; and then, to fix the colors, two coats of silicate of potash 



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