ZINC-WIIITE. 105 



flowers of sulphur, and 1 pt. salaramoniac, is heated gently 

 in a porcelain vessel, over coals, until the sulphur inflames ; 

 while burning, the mixture is stirred now and then, covered 

 with a loosely-fitting cove?, and removed from the fire for a 

 few moments. A new portion of sulphur and salammoniac, 

 without copper, is added, the cover replaced, and the vessel 

 again heated. After some time the cover is removed, when 

 much sulphur sublimes. As long as it shows a black and not 

 a blue color, sulphur and salammoniac are added, and the 

 vessel heated as before. When finished, it is washed with hot 

 water, then with a little ammonia if oxide of copper be pre- 

 sent, treated with caustic potassa or soda to remove the excess 

 of sulphur, and, finally, washed with water, ground, and dried. 

 Under a polishing tool it shows a beautiful steel-blue streak, 

 and when mixed with size and brushed on paper, a steel-blue 

 lustre on a violet-blue ground. In a medium of oil or varnish 

 it is violet-blue. 



The following simpler method was contrived in the Gewerbe- 

 Institut of Berlin. Metallic copper is precipitated by zinc 

 from a boiling solution of blue vitriol, and the fine powder 

 washed and dried. 51 pts. of this copper, mixed with 3 pts. 

 sulphur, are gently heated in a porcelain vessel, so that the 

 excess of sulphur sublimes, but does not burn. When the 

 heated mixture shows a sandy appearance it is finished, and, 

 on cooling, shows a dark-blue color. The excess of sulphur 

 is removed by potassa, and the residue well washed. If it 

 have not acquired the desired tone, it is again warmed with 

 sulphur, &c. It resists chemical action in a remarkable 

 manner. 



Winkelblech's method consists in rubbing together 1 equiv. 

 lac sulphuris and 2 equiv. metallic copper, reduced from the 

 oxide by hydrogen. 



Zinc-ivldte. — This pigment, to which attention is now drawn, 

 is either the anhydrous oxide of zinc, or a hydrated oxide, or 

 a hydrate-carbonate of the metal. It possesses a great degree 

 of whiteness, about equal to that of white-lead ; a sufficient 

 body, and, what is of great importance, is less liable to tar- 



