Lead and tlie End Product of Thorium. 



829 



due to H. Mache *. In many respects it differs from the 

 methods usually in use, and for this reason, as well as for 

 the fact that it gives consistent results, a short description 

 of the apparatus will be given. The accompanying diagram 



Fig. 1. — Apparatus for the determination of Thorium in Minerals. 



a—MoTo/f. 



b- Shaking Machine. 

 c - Calcium Chloride tube. 



d-ION TRAP. 



c-Dry pile. 



J — /on/z/it/o/v Chamber. 



<? - &ECTROMETER 

 A-M/INOMETER. 



i - Guard /?//vg 

 k —Sattery. 



shows the general arrangement of the apparatus. After the 

 solution to be tested has been obtained, it is transferred to a 

 flask of the form shown in the diagram. This is fixed to the 

 shaking machine (b) which is worked by a small electric 

 motor («). By means of an excentric rod fixed to the larger 

 wheel and to the base of the carriage of the machine, an 

 approximately horizontal to and fro motion can be given to 

 the flask and its contents. The carriage is supported on 

 either side by two springs of strip steel. Previously to 

 making a measurement, air is drawn through the solution 

 by means of a water-pump for a period of about 20 minutes, 

 the solution being in constant agitation throughout that 

 time. In this way the solution is freed from any contained 

 radium emanation. During the measurement which follows, 

 a steady stream of air is drawn through the apparatus, and 

 the shaking machine is kept constantly and uniformly 

 working. The air stream, charged with thorium emanation 

 from the solution, is first passed through a calcium chloride 



* Mache and Bamberger, Wien. Ber. cxxiii. pp. 334-345 (1914). 

 Further details will be found in the original paper. Here is also given 

 an account of Mache's aspirating method of determining radium, — a 

 method which gives very accurate and reliable results. A comparison 

 between the results given by this method and those given by the method 

 of boiling is also included. 



