Compofttion of Enamel. g 



beautiful green : but when you wifh to employ it on the raw- 

 material, you muft mix with it about two parts of its weight 

 of lilex, and bring the mixture into combination by means 

 of heat. You afterwards pulverife the mafs you have thus 

 obtained, in order to employ it. 



To obtain good white enamel, it is of great importance 

 that the lead and tin Ihould be very pur^ . If thefe metals 

 contain copper or antimony, as is often the cafe, the ena» 

 mel will not be beautiful : iron is the leaft hurtful. 



QF COLOURED ENAMELS. 



All the cqlours may be produced by the metallic oxyds. 



Thefe colours are more or Icfs fufed in the fire, according as 



they adhere with more or lefs ftrength to their oxygen. All 



metals which readily lofe thpir oxygen cannot endure a great 



degree of heat, and are unfit for being en^ployed on the rasy 



material. 



Purple. 



This colour is the oxyd of gold, which may be prepared 

 different wavs ; as by precipitating, by means of a muriatic 

 fi;lution of tin, a nit^o-n^uriat!c folution of gold much diluted 

 in water. The lealt quantity poflible of the folution of tin will 

 be fufficient to form this precipitate. The folution of tin muft 

 be added gradually until you obferve the purp'e colpur begin 

 to appear : you then (lop ; and having fuffered the colour to 

 be depofitcd,you put it into an earthen veffel to dry (lowly*. 

 The .different folutions of gold, in whatever manner preci- 

 pitated, provided the gold is precipitated in the ftate of an 

 oxyd, give always a purple colour, which w^ill be more beau- 

 tiful in proportion to the purity of the oxyd j but neither the 

 copper nor filver, with which gold is generally found allayed, 

 injure this colour in a fenfibl;; manner : it is changed, how- 

 ever, by iron. The gold precipitate which gives the moft 

 beautiful purple is certainly fulminating gold, which lofcs 

 that property when mixed with fluxes. Purple is an abun- 

 dant colour; it is capable of bearing a great deal of flux, 

 and in a fmall (juantity communicates its colour to a great 

 deal of matter. It appears that faline fluxes are better fuited 



• The colour is alwavs more bc-iutiful, if the precipitate is ground 

 with the flux before it has become dry. — Edit- 

 Vol. VII. C to 



