In the twentieth century the ninety-second element of the Periodic Table has become just about the most famous element. For it was uranium that started up the first nuclear reactor. It gave men the key to mastery of a fundamentally new type of energy.

And now uranium is produced in large quantities: the world�s production is over 40,000 tons a year. So far this is quite sufficient to meet the demands of nuclear power engineering.

But strange as it seems, not more than 5 per cent of the uranium produced is utilized directly (according to purpose). The remaining 95 per cent are called waste uranium. It cannot be used directly because it contains too little of the isotope uranium-235, the principal nuclear fuel.

But does this mean that so much labour on the part of geologists, miners, and chemists is spent in vain?

You needn�t worry: uranium has other, �non�nuclear� professions, and quite a number of them, too. Non-specialists just know very little about them, which is too bad.

Uranium has caught the interest of biologists. It has been found that No. 92 is indispensible to normal plant growth. For example, it perceptibly increases the sugar content in carrots and beets, as well as in some fruits. Uranium helps valuable soil microorganisms to develop.

Animals also need uranium. In a very interesting experiment rats were fed small amounts of uranium salts for a year. The content of the element in their organisms remained practically unchanged, and no harmful consequences were observed, but the animals almost doubled their weight. Researchers believe that uranium aids greatly in the assimilation of phosphorus, nitrogen and potassium, the most important vital elements.

Uranium in medicine? This is one of the oldest practical applications of the element. There have been attempts to use its salts for treating various diseases, such as diabetes, skin diseases, and even tumours. Nor have they been entirely unsuccessful. �Uranium therapy� is now again in the order of the day.

Uranium finds a curious use in metallurgy. Its alloy with iron (ferrouranium) is added to steel to remove oxygen and nitrogen. Steels made with ferrouranium can operate at very low temperatures. Uranium-nickel steels are very resistant even to the most aggressive chemical reagents, such as �aqua regia� (a mixture of nitric and hydrochloric acids).

Another very interesting and singular role of uranium and its compounds is that of catalysts for many chemical reactions.

Ammonia synthesis from nitrogen and hydrogen is sometimes accomplished in the presence of uranium carbide. Uranium oxide accelerates the oxidation of methane by oxygen, the production of methyl and ethyl alcohols from carbon monoxide and hydrogen, and the preparation of acetic acid. Not a few products of organic chemistry are obtained with the aid of uranium catalysts.

The chemistry of uranium is very lavish. It may be hexa-, penta-, tetra-, or trivalent in its compounds. Uranium compounds of different valence differ so greatly that its chemistry is like a combined chemistry of four different elements.

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