Composition of Enamel. 397 
put it into an earthen vessel to dry slowly.* The differ- 
ent solutions of gold, in whatever manner precipitated, 
provided the gold is precipitated in the state of an oxyd, 
give always a purple colour, which will be more beauti- 
ful in proportion to the purity of the oxyd ; but neither the 
copper nor silver, with which gold is generally found al- 
layed, injure this colour in a sensible mnnner: it is 
changed, however, by iron. The gold precipitate which 
gives the most beautiful purple is certainly fulminating 
gold, which loses that property when mixed with fluxes. 
Purple is an abundant colour; it is capable of bearing a 
great deal of flux, and in a small quantity communicates 
its colour to a great deal of matter. It appears that saline 
fluxes are better suited to it than those in which there are 
metallic calces. Those, therefore, which have been made 
with silex, chalk, and borax, or white glass, borax, and a 
little white oxyd of antimony, with a little nitre, as I have 
already mentioned, ought to be employed with it. Pur- 
ple will bear from four to twenty parts of flux, and even 
more, according to the shade required. Painters in ena- 
mel employ generally for purple a flux which they call 
brilliant white. This flux appears to be a semi opake ena- 
mel, which has been drawn into tubes, and afterwards 
blown into a ball at an enamelled s lamp. These bulbs 
are afterwards broken in such a manner that the flux is 
found in small scales, which appear like the fragments of 
small hollow spheres. Enamel painters mix this flux 
with a little nitre and borax. This matter, which pro- 
duces a very good effect, I employed, without attempt- 
ing to decompose it. It may be a very fusible common 
white enamel which has been blown into that form. It is 
to be remarked, that purple will not bear a strong heat. 
* The colour is always more beautiful, if the precipitate is ground with the 
lux before it has become dry .—Til loch. 
