[ 19 ] 
4« Having carefully purified an ounce of Silver, 
I kept it in fufion fome hours, with a finall 
quantity of glafs, and found, that the glafs, 
when cold, had formed a beautiful yellow enamel 
on the furface of the Jilver. 
5. Leaffilver laid on red hot glafs tinges \X yellow. 
When we meet with authors, who mention a 
blue or greenifii colour communicated by filver, 
the caufe mufi; have been, that the filver ufed in 
fuch procefles was mixed with copper , as it gene- 
rally is, when it is not carefully purified \p\. I 
have always found, that filver purified by the tefl 
retained fo much copper, that, when melted feveral 
times with nitre and borax, it imparted 2. green 
tinge at the firfl and fecond rnelting, though after- 
wards 710 fuch colour was obtainable fiom it. 
quick coals to neal a while •, we gave it fuch a he^ as might 
make and keep it red hot, without fufion ; and then fufrenng it 
to cool by degrees, we found that the glafs had required ss yellow 
and almofi golden colour . t i i r c 
Shaw’s Abridg. of Boyle, vol. ii. p. 98. I kajned from one of 
the chief artificers in painted glafs, that thofe of his trade colour 
it yellow with a preparation of a calx of Silver . ^ 
Kunkel’s Art of glafs, part ii. art. 49. Experiment fhews that 
it is from Silver the fineji yellow is obtained. Shaw s Lectures, 
p. c?i6. A little Silver tinges glaf yfow. .... 
Hook’s Micrographia. obf. 10. of Metalline colours. A third 
argument that the particles of metals are tranfparent is, t at 
being calcined and melted with glafs, they tinge the glafs with 
tranfparent colours. Thus the calx of ftlver tinges the glafs 
on which it is annealed with a lovely yellow or gold colour. 
r*l Merret’s Notes onNeri, c. 90. Junker, Con.pe£l:. Chem. 
tab. XXXIV. p. 889. 901. Shaw’s Abridg. of Boyle, vol. lu 
pi ' ■ COPPER. 
