I. Aluminium light alloys are all very weak for sea water corrosion. Even Duralumin, the best rolling alloy, and Silumin, one of the best casting ones, are not good on this point. Some alloys are really noncorrodible but not used for their inferior mechanical properties and diffiiculties in casting, rolling or forging. A new alloy was invented in our laboratory 6 years ago, industrial researches were completed and the products are now used in some works. It was named "Chlumin" as it contains chromium, but a few per cent of magnesium and iron are also added.
2. Non-corrodibitity. Castings of Chlumin and of an alloy of composition Cu 8%, Al 92%, the most common one, both made by metallic mould, were immersed in 5% NaCl solution. After 4 years' immersion Chlumin gave only little deposit retaining even some luster, while, the other was severely corroded precipitating considerable mass of aluminium hydroxide. The machined surfaces of Chlumin and Silumin plates were exposed to air being sprayed by salt water every day. Many black spots appeared on Silumin but Chlumin remained bright. Specimens were next immersed in 5% NaCl solution in separate bottles. The quantity of deposit and the weight decrease of specimen were measured aftea 40 days. Chlumin was a little better even than aluminium. Silumin, Y-alloy, Duralumin and all others containing Cu or Zu were attacked severely. Many test pieces of wire were immersed in 5% NuCl solution and the solution was renewed at times to expose them to air for a day to accelerate the corrosion. Chlumin and aluminium wires, annealed or not, lose scarecely their strength by 7 months' immersion. The elongation decreases in some cases. While, Duralumin, variously heat-treated or not, loses both qualities rapidly. After 5 months the strength reduces to 80 to 20% of the original value and the elongation to 50 to 20%.
3. As a casting alloy. Chlumin is a little inferior to Y-alloy in strength and yield point but is superior to it in elongation and impact resistance. It is betier than Silumin in every respect and is more easy to cast and sufe to use a8 no special process (modification) is wanted on manufacturing. Any complex form can be cast resisting to severe water pressure test. Pistons of internal combustion engine and parts of electric motor have been used for more than a year with better result than Y-alloy.
4. As a rolling alloy. Wires of Chlnmin were compaced with those of aluminium and Duralumin being allnealed at various temperatures. Duralumin aged after quenching from 510°C into water is exeedingly good indeed when annealed at temperaturs below 200°, but becomes worse than Chlumin at 300°. Besides, it may not be a safe process of manufacturing to quench an alloy of melting point of 620° from above 500°. It may be very difficult to heat a large article uniformly above 5'0°. A little overheating will set in local melting; and when the temperature is too low some parts mu t meet the worst heat-treatment. Heatin on welding will spoil the good properties given by quenching and aging and it is often impossible in practice to quench the article again. Quenched Duralumin must le worked in a few hours as it hardens with time. This a very inconvenient property and unduly treatment unavoidably some times applied ih practice will spoil the mate ial. Thus, Duralumin in actual use will not always have the best properties. Chlumin, on the other hand, needs no heat-treatment. Taking these circumstances all into account it may be concluded that Chlumin is equal in me, chanical properties with Duralumin. Thin plates, wires and articles of complex form are easily made by rolling, drawing and forging.

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Due to the protective tariff, black sheet industry in Japan has made a remarkable progress in recent years, its imports being largely replaced by home products with the consequent decline in its market prices.
The present paper is intended to review the effect of the increased tariff upon the prices of black sheet in the domestic market with special reference to domestic and foreign-made products.

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