VOL. XLVIII.] PHILOSOPHICAL TRANSACTIONS. 517 



room. They were harder to the file than the zinc at first, and fell in pieces 

 under the hammer ; without at all stretching ; which pure zinc does in a consi- 

 derable degree. 



4. TFith, Regulus of Antimony. — Regulus of antimony, the most difficultly 

 flisible of the semimetals, dissolved, in a strong fire, equal its weight of platina. 

 The compound looked of a much duller colour than the regulus at first ; and 

 broke of a close and uniform, though uneven, surface. It proved considerably 

 harder to the file, but not remarkably more or less brittle. 



On increasing the quantity of the regulus, the compound proved brighter, and 

 of a leafy texture, little different from that of the pure regulus. 

 Platina mixed ivilh Compound Metals. 

 fVilh Brass. — 1. Equal parts of platina and brass, covered with borax, and 

 Hrged with a quick fire in a blast furnace, melted perfectly together, and scarcely 

 suffered any loss. The mixture was of a greyish white colour, filed hard like 

 bell-metal, broken from a blow of the hammer, without stretching or receiving 

 any impression, and flew asunder on endeavouring to cut it with a chissel. In- 

 ternally, it appeared of a uniform fine grain, a close texture, and a darker colour 

 than on the outside. It bore a very fine polish, and did not tarnish on being 

 exposed to the air in a dry room for many months. 



1. One part of platina and 1 of brass, melted in a slow fire, lost about -^. 

 The ingot was of a duller colour than the foregoing, with a faint yellowish cast : 

 it filed softer, broke less readily from the chissel, but cracked and fell in pieces 

 under the hammer. 



3. One part of platina, and 4 of brass, covered as before with borax, and ex- 

 posed to a quick fire, melted without loss. This compound proved yellower 

 than the preceding, filed softer, bore to be cut some depth with a chissel before 

 it broke, and received some impression from the hammer, stretching a little, but 

 soon cracking in various directions. 



4. On increasing the brass to 6 times the weight of the platina, the compound 

 appeared yellower, though still very pale. It proved softer to the file ; and re- 

 ceived a greater impression from the hammer, and a deeper one from the chissel, 

 before it broke. 



5. A mixture of 1 part of platina and 12 of brass was considerably paler, and 

 much harder, than brass. It broke from the chissel ; and cracked, before it had 

 extended much, under the hammer. It bore a good polish, and was less apt to 

 tarnish than brass ; though in both respects it fell short of the compositions with 

 larger proportions of platina. 



IVith Copper and Tin. — 1. One hundred parts of platina, 34 of copper, and 

 12 of tin, covered with borax, became fluid in a strong fire, and suffered no 

 considerable loss. The ingot proved extremely hard, so as scarcely to be touched 



