SULPHATES. 



55 



brittleness the section was not highly polished. The band at 4.55 ]. is 

 complex, with a deeper one at 5 p. The same is true of the 6.4 /u, band, 

 which is complex, with a stronger band at 6.7 /A. There are slight 

 depressions at 1.9 and 3.2 p,. 



CADMIUM SULPHATE 

 (Curves a, b, c, d, fig. 42; t = o.g& and o.i mm.) 



This was an artificially grown crystal, and was perfectly transparent. 

 As a whole, it is very opaque to infra-red radiation. The band at 3 p is 

 complex, as is also the one at 4.6^, which is shown in curve d, the 

 vertical scale of which is magnified 10 times. The water bands at 1.5 

 and 2 /* are well defined, considering the opacity of the substance. 



70% 



23456 

 FIG. 41. Celestite (a) ; Ans;lesite. 



SULPHURIC ACID (H 2 SO). 

 (Curve e, fig. 42.) 



The great opacity of this substance makes it difficult for examination. 

 A film, 0.08 mm. in thickness, was pressed between two plates of cover- 

 glass, and stood over P 2 O 5 for several days. It shows no water bands, 

 while the trend of the curve at 4.5 p makes it impossible to decide on 

 the question of the SO 4 band. There is a band at 3.6 /* which is broad 

 and shallow. 



It is difficult to decide whether the frequently recurring bands at 6.2 

 and 6.5 fj. are due to SO 4 ; but it is a fact that they are very conspicuous 



