HQ COLOURS OBTAINED FROM METALLIC OXIDES. 



and may be rofe-coloured oxide of iron here fpoken of, we have a pallet 

 ide*of ironin " compofed of colours none of which are fubject to any remark - 

 this ufe, able change. This rofe-coloured oxide of iron has been long 



though this ox- known, but was not employed on- enamel, becaufe it is then 

 me ^ fubject to eoniiderable change. Or perhaps when the paint- 



ers on enamel became painters on porcelain, they continued to 

 work according to their ancient method. 



We might fuppofe that by previoufly reducing the colour 

 named carmine, already mixed with its folvent, into a vitreous 

 matter, the laft tint would be obtained. But as 1 have already 

 proved, the fire which muii be ufed to melt this vitreous 

 mafs dcftroys the red colour, Befides, it is found that, to ob- 

 tain (his colour in perfection, it is ncceffary to pafs it through 

 the fire as little as poffible. 

 Fabrication of The carmine of tender porcelain is made with fulminating 

 'gold gently decompofed, and muriate of filver; there is no 

 tin in it, which proves that it is not necelTary for the fabrication 

 of a purple colour, that the oxide of this laft metal and that of 

 gold mould be combined. 

 Violet from gold Violet is likewife obtained from the purple oxide of gold, 

 loft porcelain, ™ This colour proceeds from having a greater quantity of lead in 

 the flux, and it is nearly of the fame tint whether crude or 

 baked. 



Bat they all fail Thefe three colours totally difappear in the ftrong fire pro- 

 on hard. ' , . . . 



per to bake porcelain. 



The carmine and Carmine and purple afforded us upon glafs, only lints of a 

 ^dVon glafs- curtv violet « The violet, on the contrary, has a very beautiful 

 but the violet is effect ; but it is fubjecVto change to a blue. I cannot yet 

 beautiful. afcertain the caufe of fo lingular a change, as I obferved it for 



the firft time only a few days ago. 



(To be concluded.) 



VI. Examination 



