56 ABSORPTION OF LIGHT BY WATER CHANGED 



The results obtained with aluminium sulphate bring out the same facts 

 shown by calcium chloride and magnesium chloride, and also that water is 

 more transparent in the region l.lju and more opaque at lju. That the sul- 

 phate should not agree throughout with the chlorides is really not surprising, 

 since the sulphates show abnormal results in almost every particular. This 

 is probably due, in part at least, to the large amount of polymerization 

 which the sulphate molecules in general undergo in the presence of even 

 water as a solvent. It should also be remembered in the present connection 

 that while calcium chloride and magnesium chloride crystallize with only 6 

 molecules of water, and are therefore only largely hydrated, aluminium sul- 

 phate crystallizes with 18 molecules of water and is therefore very largely 

 hydrated. 



The results in table 11 are the radiomicrometer deflections for a solution 

 of aluminium sulphate and those for water having the same depth as the 

 water in the solution in question, and the corresponding data for potassium 

 chloride. A comparison of the two columns for potassium chloride and its 

 corresponding water shows that the two are almost equally transparent to 

 all the wave-lengths studied. 



A comparison of the aluminium sulphate with its corresponding water 

 brings out the phenomenon that we are now discussing in a very pronounced 

 manner. 



One other relation of a general character should be pointed out. The 

 curves (figs. 12 to 17) show that the addition of salt to water shifts the 

 absorption towards the longer wave-lengths. This is analogous to what had 

 already been found by Jones and Uhler, 1 Jones and Anderson, 2 Jones and 



80^ H 2 



70 



60 



50 



40 





30 i 



201 



CaCI 2 ,5.38N. 

 Depth 2 cm. 



0.9 1.0 11 12 



Fig. 12. 



' Cam. Inst. Wash. Pub. 60. 2 Carn. Inst. Wash. Pub. 110. 



