Each metabolon has a life t, so that the average life of the whole number is given by
The various metabolons from the radio-elements are distinguished from ordinary matter by their great instability and consequent rapid rate of change. Since a body which is radio-active must ipso facto be undergoing change, it follows that none of the active products, for example, the emanations and Th X, can consist of any known kind of matter; for there is no evidence to show that inactive matter can be made radio-active, or that two forms of the same element can exist, one radio-active and the other not. For example, half of the matter constituting the radium emanation has undergone change after an interval of four days. After the lapse of about one month the emanation as such has nearly disappeared, having been transformed through several stages into other and more stable types of matter, which are in consequence difficult to detect by their radio-activity.
The striking difference in chemical and physical properties which exists in many cases between the various products themselves, and also between the primary active substance and its products, has already been drawn attention to in [chapter IX]. Some of the products show distinctive electro-chemical behaviour and can be removed from a solution by electrolysis. Others show differences in volatility which have been utilized to effect a partial separation. There can be no doubt that each of these products is a definite new chemical substance, and if it could be collected in sufficient quantity to be examined by ordinary chemical means, would be found to behave like a distinct chemical element. It would differ, however, from the ordinary chemical element in the shortness of its life, and the fact that it is continuously changing into another substance. We shall see later ([section 261]) that there is every reason to believe that radium itself is a metabolon in the true sense of the term, since it is continuously changing, and is itself produced from another substance. The main point of difference between it and the other products lies in the comparative slowness of its rate of change.
It is for this reason that radium exists in pitchblende in greater quantity than the other more rapidly changing products. By working up a large amount of the mineral, we have seen that a sufficient quantity of the pure product has been obtained for chemical examination.
On account of the short life of the emanation, it exists in pitchblende in much less quantity than radium, but it, too, has been isolated chemically and its volume measured. The extraordinary properties of this emanation, or gas, have already been discussed, and there can be no doubt that, while it exists, it must be considered a new element allied in chemical properties to the argon-helium group of gases.
There can be no doubt that in the radio-elements we are witnessing the spontaneous transformation of matter, and that the different products which arise mark the stages or halting-places in the process of transformation, where the atoms are able to exist for a short time before again breaking up into new systems.
257. Radio-active products. The following table gives the list of the active products or metabolons known to result from the disintegration of the three radio-elements. In the second column is given the value of the radio-active constant λ for each active product, i.e. the proportion of the active matter undergoing change per second; in the third column the time T required for the activity to fall to one-half, i.e. the time taken for half the active product to undergo change; in the fourth column, the nature of the rays from each active product, not including the rays from the products which result from it; in the fifth column, a few of the more marked physical and chemical properties of each metabolon.
| Products | λ(sec)-1 | T | Nature of the rays | Chemical and Physical properties of the product |
|---|---|---|---|---|
| Uranium | — | — | α | Soluble in excess of ammonium carbonate, soluble in ether. |
| Uranium X | 3·6 × 10-7 | 22 days | β and γ | Insoluble in excess of ammonium carbonate, soluble in ether and water. |
| Thorium | — | — | α | Insoluble in ammonia. |
| Thorium X | 2·0 × 10-6 | 4 days | α | Soluble in ammonia and water. |
| Emanation | 1·3 × 10-2 | 53 secs. | α | Chemically inert gas of heavy molecular weight. Condenses at -120° C. |
| Thorium A | 1·74 × 10-5 | 11 hours | no rays | Deposited on bodies; concentrated on the cathode in an electric field. Soluble in some acids; Th A more volatile than Th B; shows definite electro-chemical behaviour. |
| Thorium B | 2·2 × 10-4 | 55 mins. | α, β, γ | Same |
| ? | — | — | — | |
| Actinium | — | — | no rays | Insoluble in ammonia. |
| Actinium X | 7·8 × 10-7 | 10·2 days | α (and β?) | Soluble in ammonia. |
| Emanation | ·17 | 3·9 secs. | α | Behaves like a gas. |
| Actinium A | 3·2 × 10-4 | 36 mins. | no rays | Deposited on bodies; concentrated on the cathode in an electric field, soluble in ammonia and strong acids; volatilized at a temperature of 100° C., A and B can be separated by electrolysis. |
| Actinium B | 5·4 × 10-3 | 2·15 mins. | α, β, γ | Same |
| ? | — | — | — | |
| Radium | — | 1300 years | α | Allied chemically to barium. |
| Emanation | 2·1 × 10-6 | 3·8 days | α | Chemically inert gas of heavy molecular weight; condenses at -150° C. |
| Radium A (active deposit of rapid change) | 3·85 × 10-3 | 3 mins. | α | } Deposited on surface of bodies; concentrated on cathode in electric field; soluble in strong acids; B volatized at about 700° C., A and C at about 1000° C. |
| Radium B (same) | 5·38 × 10-4 | 21 mins. | no rays | Same |
| Radium C (same) | 4·13 × 10-4 | 28 mins. | α, β, γ | Same |
| Radium D (active deposit of slow change) | — | about 40 | no rays | Soluble in acids; volatile below 1000° C. |
| Radium E (same) | 1·3 × 10-6 | 6 days | β and γ | Non-volatile at 1000° C. |
| Radium F (same) | 5·6 × 10-8 | 143 days | α | Deposited on bismuth from solution; volatile at about 1000° C., same properties as radio-tellurium and polonium. |
The products and their radiations are indicated graphically in [Fig. 102] on page [448].