Badio-adivity of Uranmm. 



421 



third radio-active body in pitchblende. In the ' Comptes Eendus ' for 

 October 16, 1899, and April 2, 1900,*M. A. Debierne describes a radio- 

 active body, to which he gives the name of "Actinium." At first 

 he Sciid "actinium" showed the principal analytical properties of tita- 

 nium, but later he describes it as not resembling titanium in all its reac- 

 tions. M. Debierne gives many reactions of the new substance, and in 

 some instances they are like those of radium. But he qualifies them by 

 the statement that they cannot yet be considered as belonging definitely 

 to the new radio-active substance, because up to the present it has not 

 been obtained sufficiently concentrated. He believes rather that these 

 reactions should be looked upon as the result of retention, analogous, 

 to that of iron oxide by barium sulphate. He says that the chemical 

 reactions of the most active substance which he obtained, together 

 with its spectroscopic examination, showed that it chiefly consists of 

 thorium. He cannot, however, be sure that it resembles thorium in 

 all its reactions. 



37. Experiments have been commenced to see if it is possible ta 

 separate thorium compounds into an active and an inactive body. A 

 strong solution of thorium sulphate was slightly acidulated with sul- 

 phuric acid, and gradually raised to the boiling point. A copious 

 precipitate of sulphate came down, and was filtered hot. The pre- 

 cipitate was dissolved in cold water, and the solution re-heated,. 

 when a precipitation of the sulphate again occurred. The mother- 

 liquor from one crystallisation was added to the crystals from another 

 in the systematic manner adopted in fractionation, and when the opera- 

 tions had proceeded some time a test was made on the " head " and 

 " tail." A small quantity of solution from each was evaporated to 

 dryness and strongly ignited before the blowpipe. The two lots of 

 earth were put in cells and a sensitive plate exposed to their action 

 for seventy-two hours. On development not the slightest diff"erence 

 could be detected between the impressions produced by either of the 

 fractions. 



I next tried partial crystallisation of thorium nitrate, fractionating 

 it in the way already described in the case of uranium (15). Great 

 difficulties were here encountered, owing to the tendency of a strong 

 solution of thorium nitrate to remain supersaturated for several days, 

 when it would suddenly crystallise to a solid mass. After some 

 weeks, however, six fractionations were effected, and tests were made 

 on the first and last of the series. 



The sensitive plate was exposed to their action for 120 hours. On 

 development, the fraction at the first end (crystals) gave a very feeble 

 action, while that at the other end (mother-liquors) gave an impres- 

 sion about three times as intense. This points to the possibility of 

 separating from thorium its radio-active substance. 



By the kindness of Dr. Knofler, of Berlin, who makes thorium 



VOL. LXVI. 2 I 



