5t)6 Receipts for Ennmcl Colours, 



IVhile Oxide of Tin. 

 Into a small wooden box witli a sliding cover, chalked over on 

 the inside^, pour melted tin fioin a iadle, and shake the box till 

 the tin becomes finely granulated ; then wash it and dry it, and 

 put it into a Florence oil ilask, and pour over it strong; nitrous 

 acid, which rapidly converts it to a white powder. When a suf- 

 ficient quantity of this is obtained, it should be well washed in 

 several boiling waters-, poured out into a bason, and dried before 

 the fire ; — -it then produces a very white oxide of tin. 



Black Oxide of Col alt. 

 Take good metallic cobalt*, and dissolve it to saturation in 

 nitric acid diluted with a little water, in a ilask placed in sand over 

 the fire ; then pour it in a large bason, and having added a quan- 

 tity of xvater, pour in a solution of subcarljonate of soda, as long 

 as any precipitate falls down: wlien settled pour ofif the water, 

 and wash the powder in several hot waters, filter it and dry it. 

 When dry, mix it in a biscuit-ware mortar with a pestle of the 

 same, with three times its weight of dry nitre ; place it in a warm 

 Crucible, and drop in an ignited piece of charcoal: some slight 

 explosions will then take place, and when these have ceased, 

 make the calx red hot: this, after being washed and dried, pro- 

 duces the best oxide of cobalt for enamel, and capable of making 

 and compounding various colours. 



Fluxes. 



Take great care to mix all the ingredients accurately together 

 in a biscuit-ware mortar, with a pestle of the same, and to have 

 them all pounded as fine as possible. Let the crucibles be made 

 warm before the fluxes are put into them, (by placing them on 

 the fire with the open end downwards,) which will prevent most 

 of the accidents which happen by their breaking in the fire. 



The best furnace for making fluxes, or for any other process 

 that requires great or continual heat, is a common German stove 

 about 18 or 20 inches inside, lined all round from the grating to 

 the top, (except the aperture at the door in the front for the oc- 

 casional introduction of a muffle,) with one row of fire-bricks set 

 with loam ; the iron-pipe chinmey projects from the back part 

 near the top. The top or cover of the furnace, to be loose like 

 a lid, and removable by handles ; in tlie centre of it a circular 

 hole is cut out, which is also fitted with a cover through which 

 the top of the crucible may be lifted off, and its contents be 

 stirred up with a bar of steel. A small piece of fire-brick is 

 placed on the grate, for the crucibles to stand on, and the fuel 

 should be charcoal and coke mixed, or charcoal alone. 



* in the choice of cobalt, that which when dissolved in nitric acid gives 

 the purest and deepest red solutioa generally makes the finest colours. 



placed 



