334 Prof. McCoy and Dr. Yiol : Chemical Projierties and 



' The Chemistry of the Radio-Elements,'' appeared *. This 

 is a comprehensive review of published knowledge of this 

 subject, but does not contain new material. In view of this 

 resume, we shall not dwell upon the historical aspects of the 

 subject ; we shall, however, include our results and con- 

 clusions which have previously been reported by others. In 

 most cases our statements here are put in generalized form 

 rather than as records of specific experiments. This is done 

 on account of the very numerous separate experiments made 

 during a period of three years. 



The members of the thorium series with the symbols (or 

 abbreviations) here used are as follows : — Thorium ; meso- 

 thorium-one (Msj) ; mesothorium-two (Ms 2 ) ; radiothorium 

 (Rt) ; thorium X (ThX) ; emanation (Em) ; thorium A (A) 

 of period 0*145 sec. ; thorium B (B) of period 10'6 hours ; 

 thorium C (C) of period 60' 8 minutes ; thorium D (D) of 

 period 3*1 minutes f. The product C is doubtless complex J, 

 the components being C : and C 2 . 



Mesothorium-one. — Mesothorium-one is easily separated 

 from thorium. So far as is now known, all reactions which 

 separate ThX from Th also separate ~Ks 1 ; for it seems that 

 the latter and ThX have essentially identical chemical 

 properties. We have studied the following methods of 

 separation of Ms x from Th : — 



(1) When a dilute solution of thorium nitrate is precipi- 

 tated by ammonia either in large or small excess, the greater 

 part of the Ms ]? 80 or 90 per cent., remains in the filtrate. 

 This is a well-known reaction §, which we have regularly 

 used in practice. 



(2) Thorium nitrate is precipitated by a solution of sodium 

 carbonate, but redissolves in an excess, the solubility being 

 greater in the presence of some bicarbonate. For example, 

 5 g. of thorium nitrate redissolve completely in a solution of 

 5 g. of anhydrous sodium carbonate and 2 g. of sodium bi- 

 carbonate in 50 c.c. of water. If 2 or 3 mg. of ferric chloride 

 in dilute solution be added, it will be precipitated as basic 

 carbonate if the solution be warmed to 70° or 80°, and carry 

 down all of the Msj and all ThX present as well. In a 

 similar manner, any barium present in the thorium solution 



* Longmans, Green & Co., London and New York, 1912. 



t Hahn & Meitner, Verh. d. Phys. Ges. xi. p. 55 (1909). On account 

 of the recent changes of nomenclature, which we follow, we wish to 

 avoid all uncertainty bv mention of the periods. 



% Hahn, Phys. Ze.it. vii. pp. 412, 456 (1906). Barratt & Marsden, 

 Proc. Phys. Soc. Lond. xxiv. p. 50 (1911). Geiger & Nuttall, Phil. Mag. 

 [6]xxii.p. 613 (1911). 



S Boltwood, Am. Jour. Sci. [4] xxv. p. 93 (1907). 



