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with. As far as time permitted, his mode of doing so was that just indicated. In a few instances the outlines then accumulated have been filled in, and an orderly arrangement of the material made, so that it might be as useful as possible in the laboratory.

If each element were dealt with in such a manner, the accumulated result would save much vexation and laborious search. This, in time, some industrious person, free from the necessity of earning a living, may do. Meanwhile this booklet, by the manner in which it is received, may assist one to decide whether more of a like kind are desirable, or whether the author is mistaken in the general usefulness of the plan.

THE ANALYTICAL CHEMISTRY

OF URANIUM

INTRODUCTORY NOTE.

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URANIUM was discovered by Klaproth in 1789, but the actual metal was isolated by Peligot in 1842 ; what had previously been regarded as the metal was really its lower oxide (UO,).

The ore occurs in Saxony, Cornwall, and America, but the deposits are generally of a very sparing character.

The Cornish mine at St. Stephen's, where ore (mostly uranic phosphate) is said to occur in a continuous lode from 3 to 5 feet thick, is exceptional.

Uranium is closely related (chemically) with chromium, molybdenum, and tungsten. These latter metals have each an acid-forming trioxide ; the trioxide of uranium, however, acts both as an acid (sodium uranate) and a base (uranyl nitrate). Early papers on the chemistry of uranium are unintelligible unless one bears in mind, not only that the protoxide was mistaken for the metal,

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but also that the atomic weight of the metal has been doubled in recent times.

Uranous oxide is formed by heating U,O in hydrogen.

It is the base from which the unstable uranous salts are derived, e.g. U(SO.)2.

Uranic oxide unites with strong bases to form uranates which have a composition analogous to dichromates, e.g. Na,U,O, (sodium uranate). But it also acts as a base in the formation of uranyl salts ; e.g. UO,SO, and UO,(NO3)2

Uranoso-uranic oxide occurs in nature as pitchblende, and may be prepared artificially by heating any oxide in air or oxygen.

When digested with nitric acid it dissolves to UO,JNO2)2. and this salt by limited ignition is converted to the trioxide, of which it is a derivative. When U,0, is very strongly ignited it loses oxygen, and passes to U,O; ; this, it is surmised, is the change. which takes place — with the formation of an intense black colour — when porcelain painted with the uranic glaze is fired.

Higher oxides, which give rise to peruranates, are formed by adding hydrogen peroxide to uranyl solutions. These have been investigated by Fairley and others, and made use of to a limited extent in the analysis of uranium compounds.

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