Relative Activities of Radio-Products of Thorium. 335 



will also be left as insoluble carbonate containing, in the 

 absence of iron, all of the Ms x and ThX. 



(3j The precipitation of barium as sulphate in a thorium 

 nitrate solution is not complete ; but when the concentra- 

 tions of barium salt and sulphuric acid are sufficient to form 

 a precipitate, the latter carries down Msi more or less com- 

 pletely. For example, O'l g. of barium sulphate removed all 

 of the Ms | from 5 g. of thorium nitrate in 100 c.c. of water. 



(4) The precipitation of thorium by oxalic acid does not 

 give a definite separation of Ms x from thorium. In strongly 

 acid solutions much of the Ms x is left in the filtrate ; in a 

 neutral solution, if the precipitate is allowed to settle out for 

 one or two days, most of the Msj is found in the precipitate. 



A solution of Msx which has been separated from 

 thorium nitrate by ammonia shows the following chemical 

 behaviour : — 



(1) By the addition of a small amount of ferric chloride 

 (5 mg. for 100 c.c), and then an excess of sodium 

 carbonate, the whole of the Ms, is thrown down with the 

 precipitate formed when the solution is boiled. 



(2) If the iron, as in (1), is precipitated by ammonia, the 

 Msj is only partially precipitated, the fraction increasing 

 with the amount of iron and presence of carbonate. 



(3) Calcium carbonate, formed by the use of ammonium 

 carbonate, carries down Msj completely. 



(4) Mesothorium-one and barium are inseparable by any 

 known chemical reactions ; if barium be separated from any 

 mixture it will be found to contain all of the Ms x *. Accord- 

 ing to Soddy t fractional crystallization of barium chloride 

 leads to an enrichment in Ms l5 just as in the case of radium. 



(5) Ms! is not appreciably carried down with aluminium 

 hydroxide when the latter is precipitated by pure NH 3 , free 

 from carbonate. We use the gas obtained by warming con- 

 centrated ammonia to which barium chloride has been added. 



(6) Ms x is not carried down with lead sulphide precipitated 

 by hydrogen sulphide (in acid solution), and very probably 

 also with no other sulphide under like conditions. 



The Msi used in our earlier experiments was obtained from 

 thorium nitrate by precipitation of the thorium by ammonia. 

 The til rate always contained both ThX and Msi, as the two 

 are identical in chemical behaviour J. Since Ms x is itself 

 inactive, its presence in such a case is established after the 

 decay of ThX by means of the activity of the Rt, &c, which 



* Soddy, Trans. Chem. Soc. Loud. xcix. p. 72 (1911). 

 t Ibid.' See also Marckwald, Ber. d. Chem. Ges. xliii. p. 3420 (1910). 

 % Marckwald, loc. cit. Soddy, loc. cit. 



2 A2 



