ROENTGEN ABSORPTION HISTOSPECTROSCOPY 



133 



thickness is 1 />.. The data in the table have been used to obtain the 

 curves in Figure 20, and from these it appears that sections 0.2-0.3 

 mm. thick are appropriate for potassium analysis. Thus, in a volume 

 of 0.001 fx\. of muscle tissue having a surface of 0.01 mm.- and a 

 potassium content of 0.3% the quantity analyzed will be 3 X 10"^ g. 



Fig. 21. Schematic picture showing the arrangements for analysi.s in a 

 microcuvette : S, slit in roentgen tube; C, the crj^stal; K, the microcuvette, 

 F, the photographic fihn. In place of K a microscopic section can be used. 

 From Engstrom (1946) 



Fig. 22. Roentgen tube for primary excitation. 

 From Engstrom (1946) 



3. Apparatus 



The arrangement shown in Figure 21 enables the simultaneous 

 determination of the incident and transmitted radiation intensity. 

 The former is proportional to the blackening on the upper part of 

 line L, and the latter to the lower part. The roentgen tubes employed 

 by Engstrom to produce the radiation were operated by a direct- 

 current unit manufactured by G. Schonander Co., Stockholm. This 



