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974, October, I917.)--Owing to the great scarcity of platinum and its consequent high price, platinum substitutes l'mve been eagerly sought, particularly within the last three or four years. From what has already been accomplished in this direction it is evident that llo single metal or combination of metals will fully take the place of platinum. The alloy of gold with palladium affords a partial substitute for crucibles and dishes, and perhaps more nearly replaces platinum in this respect than anything yet offered. The price of this alloy, however, is comparatively high, though, bulk for bulk, it is only about half as costly as platinum. The alloy of nickel with chromium, the silicon-iron alloys, and pure quartz have also given satisfactory results for certain laboratory purposes.
The stellite alloys are not fixed or definite in their composition, but may be divided broadly into two classes: (~) those malleable at red heat, and (2) those that can be worked into the desired form only by casting. The malleable alloys are composed almost entirely of cobalt and chromium, and the proportion may vary from IO to 5o per cent. of chromium, with a corresponding varia{ion of the other constituent. These alloys are very hard and resist nitric acid almost perfectly, even when boiling, particularly if the chromium content is over 15 per cent. They forge with difficulty at temperatures varying from 75 ยฐo to I2OO ยฐ. They have been forged into table ilnplements, cutlery, chemical apparatus, and jewelry.
The malleable alloys are all slowly attacked by either hydrochloric, sulfuric, or hydrofluoric acid, but are nearl{, immune to all chemical combinations, as well as t~ the fruit acids. _ks evaporating dishes made of this metal take a bright polish, and can be made of comparatively light section, they will prove suitable for eval)orating many chemical salts to dryness, and particularly suitable for boiling the caustic alkalies. Substances may be evaporated to complete dryness in these vessels without danger of breakage, since the tensile strength of the alloy exceeds ioo,ooo pounds per square inch. The vessels retain their lustre under practically all chemical laboratory conditions. The alloy also gives most excellent results in the form of lamp stands, supporting rings, triangles, etc. They can be heated to full redness without the formation of scale, and subjected to temperatures up to ~2oo ยฐ C., and still retain considerable strength. ]in fact, the stellite alloys possess the highest " red hardness " of any of the alloys yet discovered.
In many cases stellite may be substituted to great advantage for I54
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