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I 24 When this mixture Ina cold, I feparated from it, by a magnet. (mall grains of iron. weighing about one twentieth part of the

hours to a red heat. fend.

Exp. 3. I melted find thus irpreuni of if

with half its weight of borax and the fame quan-

tity of nitre. and found that it produced a perredly co/ouch:II and tr.infparent glafs.

Exp. 4 To two parts of the white rand ufcd in making cryftal eats, and one of borax and nitre. I added a twentieth part in weight, of the grains wlnch I had extraded from the fand by

Exp. a. and having vitrified this compofition. I found that it was become exaCtly fundar in colour, to that commonly ufed in making green gluts. Exp. 5. I expofed feversl pieces of green bottle 00 made at dilferent glafs-houfes, under a muffle, to a drong fire, for the (pace of half an hour, and found that they were all become 6Ixe. If the crocus of iron is added in too great a pen-

portion, it continues to adhere together. and remains unmixed, or at lead imperfedly mixed, with she _glafs, retaining for that reafon the colour

natural to it when undiflblvedy or if it be in

(mailer quantity, though yet in too great proportion to be diffolved, it will make forne intermediate colour between the roulay and the Blue, which left it always imparts, when Ea a fulflcient degree of fire and a proper proportion. The necellity of a due proportion of metal to the glafs has

been already inftanced in gold, which if in too large a proportion to be didolved by the glafs, infiend

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