340 Prof. McCoy and Dr. Yiol : Chemical Properties and 



(5) They are also carried down from slightly acid solutions- 

 by lead iodide or lead chromate. 



(6) They are carried down when added ferric iron is pre- 

 cipitated by an excess of sodium carbonate or by ammonium 

 acetate as basic acetate. 



(7) They are carried down by bismuth oxy chloride formed 

 when bismuth chloride is added and the solution diluted. 



(8) B and C are not carried down by mercuric iodide or 

 silver chloride. 



We can confirm the statements of Moore and Schlundt * 

 that B and are separated by the following reactions : 



(9) Barium or lead sulphate precipitated in a solution of 

 B and C carries clown B completely and C only partially. 



(10) Ferric iron precipitated by pyridine carries down 

 but not B. 



(11) Ferric iron precipitated by fumaric acid from a. 

 boiling nearly neutral solution of B and C carries down all 

 of the C and only a small part of the B. By three or four 

 repetitions of the precipitation we have obtained C in which 

 we could not detect any B after the complete decay of the 

 former. The method seems to leave nothing to be desired 

 as a means of preparing pure C. It is. of course, under- 

 stood that the product so obtained contains the two com- 

 ponents Ci and C 2 , and, in addition, the beta-ray product D r 

 which has a period of 3'1 minutes, and which will there- 

 fore accumulate rapidly in C even if it were removed by 

 the treatment described. 



In carrying out the reactions here recorded, in solutions 

 of thorium free radio-products, the amount of precipitate 

 waSj as a rule, 10 to 50 mg. for 100 c.c. of the solution. 

 In some cases, especially those in which the active substance 

 is divided between precipitate and filtrate, the proportion of 

 active substance carried down depends on the amount of the 

 precipitate. The identity of each radio-product studied was 

 fully established by means of the nature of its rays and its. 

 rate of decay. 



II. The Ratio of the Activity of Thorium B+ C+D to 

 that of Thorium X. + Emanation + A. 



A knowledge of the relative activities of the equilibrium 

 proportions of the active products in a given series is of 

 importance for investigations in radioactivity. The problem 

 has been pretty completely solved for the uranium-radium 



* Trans. Am. Electrocliem. Soc. viii. p. 269 (1905)- 



