ROENTGEN ABSORPTION HISTOSPECTROSCOPY 



137 



the beam when the ionization chamber is used. Adjustments on the 

 circular scale can be made to some hundredths of a degree, and stops 

 on the scale can be set to enable rapid and accurate changes for 

 different wavelengths. 



The construction of the metal microcuvette is shown in Figure 25. 

 The walls in the direction of the radiation are made of thin aluminum 

 foil, glass, or cellophane sheets. The cuvette capacity is 0.2 fx\. or 

 greater. Crystals of calcite (d = 3029 X.U.) and rock salt 

 (d = 2814 X.U.) were used and the ionization chamber was 

 charged to 150 A'olts. 



10 cm 



Fig. 26. Vacuum spectrograph for histochemical analysis. 

 From Engstrdm (1946) 



Vacuum Spectrograph for Tissue Analysis. The construction 

 of the vacuum spectrograph is shown in Figure 26. The roentgen 

 tube (yi) is joined to the spectrograph by an air-tight rubber gasket. 



