l8 Colouring properly of the Oxide of Molyhdena. 



of the wool, that the ftnflfhad all the appearance of wool dyed 

 with indigo. After this fuccefs, M. Jaeger endeavoured to 

 unite the colour of molybdona with other vegetable colours, 

 and to tranfport it in that flale to (luffs. The refults of this 

 labour were as follow : 



F. Difi'erent fliveds of woollen cloth, to which a greater or 

 lefs blue colour had been communicated by tinfture of mo- 

 Jvbdena, were boiled for half an hour in a cold aqueous in- 

 fufion of quercitron bark. They acquired different fliades of 

 green, but which did not poffefs all the purity and uniformity 

 wiiich could have been wiflied. He therefore thought that 

 it \voidd be ncceliary to change a little his proeefs. 



G. Different (lireds of woollen ttuff were boiled for a longer 

 or fhorter time in an infufion of quercitron bark, with a view 

 to communicate to them dilferent (hades of yellow. The 

 quantity of blue tinfilure necciTary for each (Lade of yellow, 

 beginning with the weakefl, was added to the infufion, which 

 was in a great part cxhau(led. In this manner, (hades of 

 green, not inferior in beauty to Saxon green, were obtained 

 by an ebullition of half an hour. 



H. In other experiments, fomctimes the blue tincture and 

 fometimes the molybdale of potafh w'as tried, either by com- 

 bination with vegetable colours, or alone, as mordants or mo- 

 difiers. The refults in general were very fatisfaftory. Several 

 of the colours thus obtained were fo fixed and unalterable in 

 the fun and air, and by ftrong acids, that no other colour 

 could be compared with them in this rcfpeft. 



M. .Taeger terminates his interefting labour by announcing 

 a black colour, furniflied to him by a compofition of molyb- 

 date of potafli, acetite of alumiue, and logwood. This black 

 having been tried, in regard to durabilitv, as compared with 

 common black, bv boiling both for a quarter of an hour in 

 diluted fulphuricacidjlhatofmolvbdena was fcarcely changed, 

 while the other loft its colour entirely, and paffed to a burnt 

 yellow. 



The author adds alfo, that the blue tin6lure of molybdena, 

 evaporated in a gentle heat, furnifhed a very fine blue, folu- 

 ble in water, which might be ufed for writing, and even for 

 painting, in the faine manner as any other colouring jpice. 



It appears from thefe experiments that molybdena may be- 

 come a very valuable colouring matter in the art of dyeing. 



V. Be 



