M. TECHNOLOGY. 531 



temperature, because fuchsine, when cold, precipitates in 

 amorphous insoluble flakes, which melt, when heated, into 

 lumps of a greenish metallic lustre. Filtering does not re- 

 store the efficiency of the dye thus spoiled. 5 0, xx., 160. 



PALE NANKIN YELLOW. 



To obtain a pale Nankin yellow color on cotton or woolen 

 cloth, the fabric is to be boiled in water for half an hour, and 

 allowed to drain, and then immersed in a bath of perman- 

 ganate of soda of one degree Baume, heated to 86 Fahr. It 

 is to be removed at the end of half an hour, and, after allow- 

 ing it to drain, it is to be immersed in a bath of sulphate of 

 iron, to fix the color. This latter bath should contain ten 

 per cent, of the amount of water employed in the first bath. 

 The cloth is then to be washed, next introduced into a bath 

 of sulphurous acid of one degree Baume, and finally washed 

 and dried. 4 B, July, 570. 



NEW MODE OP DECORATIVE PAINTING. 



A new process of decorative painting has lately been an- 

 nounced to the Paris Academy. This consists in the use of 

 a sheet of tin-foil, as thin as possible, and, consequently, of 

 great flexibility. The tin-foil is stretched upon a hard and 

 smooth ground, such as glass, and upon the foil a painting 

 is made of any kind, whether of uniform tint or decorated. 

 The painting is to be allowed to dry, and it is then varnished 

 and the tin-foil removed from the glass, when it is ready for 

 further application. Before being applied to any surface, a 

 water-proof coating is to be given to the latter. The tin is 

 then applied by means of some kind of cement, and made to 

 accommodate itself to any curvatures of the surface that may 

 exist. The tin-foil can be used upon wood, plaster, or stone. 

 6 B, May 6, 1229. 



GOLD POWDER FOR GILDING. 



Gold powder, for gilding, may be prepared by putting into 

 an earthen mortar some gold leaf, with a little honey or thick 

 gum water, and grinding the mixture till the gold is reduced 

 to extremely fine particles. When this is done, a little warm 

 water will wash out the honey or gum, leaving the gold be- 

 hind in a pulverulent state. Another way is to dissolve pure 



