264 ANNUAL OF SCIENTIFIC DISCOVERY. 



M. Kuhlmann in the course of his investigations has submitted the silicified 

 stones to a true process of dyeing, by impregnating them in the first instance 

 with certain metallic salts, which by precipitation would produce the required 

 color. Thus by impregnating the stones with salts of lead or copper, and then 

 exposing them to sulphureted hydrogen gas, or a solution of sulphuret of ammo- 

 nium, he obtained at pleasure different shades of gray, black, or brown. With 

 the salts of copper and ferrocyanide of potassium, I obtained a copper color, 

 etc. In this connection was observed a fact, which in a theoretical as well as 

 practical point of view, is not without interest. M. Kuhlmann found that por- 

 ous limestones, and all other bodies of similar composition, when boiled in a 

 solution of a metallic sulphate, the base of which is insoluble hi water, gives 

 rise to the disengagement of carbonic acid, and the fixing to a considerable 

 depth of the metallic oxyd in intimate combination with sulphate of lime. 

 "When the metallic sulphates contain colored oxyds, we thus obtain very beau- 

 tiful tints of different colors. Thus with sulphate of iron we get a rusty color, 

 more or less deep, according to the degree of concentration of the solution. 

 Sulphate of copper gives a beautiful green color ; sulphate of manganese a 

 brown ; and a mixture of sulphates of iron and copper, a chocolate. The af- 

 finities which determine these reactions must be very powerful for the metallic 

 oxyds of the sulphates to be so completely absorbed by the carbonate of lime, 

 that with some oxyds, such as that of copper, there remains not in the solu- 

 tion, after boiling in. with excess of chalk, a trace appreciable by the most 

 delicate tests. In this way corals and shells may be colored with a great va- 

 riety of tints. Comptes Eendus. 



Another step taken by M. Kuhlmann was the application of alkaline 

 silicates, to painting; and instead of oils and the ordinary vehicles, he 

 uses a concentrated solution of silicate of potash, finding it to work well with 

 vermilion, ultramarine-blue, the ochres, oxyd of chrome, and some others. 

 These colors applied to a wall become, so to speak, part of its substance and 

 almost imperishable. Prepare your wall, paint it of any color, then sprinkle 

 the whole surface with a solution of silicate of potash, or soda, and you cover 

 it with a permanent glaze. Advantage has been taken of this discovery in 

 the decoration of public buildings in Germany, with the happiest effects. 



Yv r ood, affected as it is by moisture, is not so well adapted for the silicated 

 colors as brick or stone. The most suitable kinds, according to M. Kuhlmann, 

 are ash and horn-beam. But glass, porcelain, and metal, if quite dry, take 

 the colors readily. In glass particularly, a semi-transparency is obtained, 

 which renders it applicable, at low cost, to the windows of private houses or 

 of churches ; and we all know what admirable effects can be produced by 

 colored panes artistically introduced. At this point the author makes the fol- 

 lowing practical remarks: "Artificial sulphate of baryta, applied by means 

 of the silicate of potash to glass, gives to the latter a milk-white color of great 

 beauty. The sulphate becomes intimately incorporated with the silex, and 

 after a few days can not be washed off even with hot water. On subjecting 

 the glass thus painted to the action of an elevated temperature a beautiful 

 white enamel is produced on the surface, which would economically replace 

 the enamels that have oxyd of tin for their base. Ultramarine-blue, oxyd of 



