5 



INFRA-RED TRANSMISSION SPECTRA. 



Alum Solution. 

 (Saturated solutions at o C. ; cell i cm. thick; fig. 32.) 



In fig. 32 are given the transmission spectra of water (0-0-0-0) and 

 of solutions of the alums of potassium (x-x-x), ammonium (_.__), and 

 of ammonium-iron. The curves are due to E. F. Nichols 1 and are in- 

 cluded here because of their bearing upon the present data. The trans- 

 mission curves of the solutions of potassium and of ammonium alum are 

 identical with that of water. The ammonium-iron alum [(NH 4 ) 2 Fe 2 (S0 4 ) 7 ] 



80 



5 .7 9 /. / 1.4-jU 



Fig. 32. Water 0-0-0; Potassium alum 

 x-x-x; ammonium alum --.-.; ammo- 

 nium iron alum (lowest curve). 



shows greater opacity, which from the trend of the curve appears to extend 

 into the visible spectrum, due perhaps to a trace of iron oxide which is 

 avoided with difficulty. The transmission curve of a clear plate of alum 

 4 mm. in thickness is shown in curve a, fig. 33. 



Borax and Potassium Permanganate. 

 (Cell 1 cm. thick; glass walls; fig. 33.) 



In fig. 33 are given the transmission curves b of borax (Na 2 Br 4 7 ) and 

 curve d of potassium permanganate (KMnOJ. The latter solution was 

 not saturated. The results show that there is no increased absorption of 

 the solution over that of pure water, except in permanganate, which, of 

 course, is almost opaque to the visible. 



Lanthanum Nitrate (LaNOs); Didymium Nitrate [Pr,Nd(NC>3);i]; 



Sulphuric Acid (H 2 S0 4 ); Liquid Glass (NaiSiOs). 



(Cell 1 cm. Concentration of nitrates unknown. Fig. 34.) 



In fig. 34 are given the transmission curves, a of sulphuric acid, b of 

 lanthanum nitrate (solution), c of didymium nitrate (solution), and d of 



1 E. F. Nichols: Phys. Rev., 1, p. 1, 1896. 



