26 



INFRA-RED TRANSMISSION SPECTRA. 



energy is transmitted beyond 3 /A; even the water bands at 1.5, 2 and 3 

 are almost obliterated. As the examination proceeds it will be noticed 

 that this opacity appears to be a property of the borates. 



CALCIUM CHLORIDE (CaCl 2 +6H 2 O). 

 (Film melted between rock-salt plates, t = 0.1 mm. Fig. 10.) 



This compound comes in large hexagonal crystals. A specimen was 

 melted between two plates of rock salt, and stood over P 2 O 5 for several 

 days, until the edges became white from dehydration. The substance 



90%, 



10 



I Z 3 4 5678 



FIG. 10. Calcium chloride (a); Potassium ferrocyanide. 



recrystallized in the meantime and when examined showed the water 

 bands in their usual position and intensities except the 3 p band, which 

 is shifted to 3.2 yu.. 



POTASSIUM FERROCYANIDE (K4Fe(CN),+3H 2 O). 

 (Section split parallel to c; transparent; = 0.3 mm. Fig. 10.) 



The water is so easily expelled from this mineral that the heater had 

 to be used on 70 volts. The transmission curve shows the water bands 



