SOLUTIONS. 



101 



sulphates examined shows that they are not present exclusively in those 

 sulphates containing water of crystallization. In other words, they are 

 due to the SOj radical, and not due to hydrous sulphates, as might be 

 inferred from the study of sulphuric acid. Concentrated sulphuric acid 



7 8 9 10 



FIG. 84. Sulphuric acid. 



\Z 



contains SCX, and it is interesting to note that the 10.4^ band, which 

 in a previous examination of gases was found in SO 2 , is one of the 

 strongest here, and, as will be noticed in Appendix II, disappears on 

 diluting the acid. 



CADMIUM SULPHATE (CdSCX). 

 (Saturated, and dilute 1 A H 2 O solutions. Fig. 85.) 



The reflecting power is, of 

 course, much lower for solu- 

 tions. Curve b shows that the 

 reflection band is asymmetri- 

 cal. The maximum occurs at 

 9.2 //,. The absorption band at 

 4..6 /*, is harmonic with this one. 

 This reflection band was found 

 by Pfund 1 for the solid crystal 

 at 9.1 /u, more nearly 9.15^, 

 as read on the published curve. 



o 

 It 



a 3 10 



FIG. 85. Cadmium sulphate. 



\\JU 



Water has no reflection bands in this region. 



NICKEL SULPHATE (NiSC>4+7H 2 O). 



In fig. 86 are given the curves (a) for a saturated solution of NiSO 4 , 

 and (b) for a solution diluted to about one-half, while curve c is for a 

 large, solid crystal which was not highly polished. The curves for the 



1 Pfund : Paper presented at the meeting of the Amer. Phys. Soc., April 20-22, 

 1906. 



