564 wick. 



and the shift amounts to from 3 to 6 Angstroms. This band is sharply 

 defined at normal pressure and its appearance is not perceptibly 

 changed by pressure. 



The most conspicuous effect of pressure is that shown upon the 

 prominent group of bands at 5800. In the photographs taken at 

 normal pressure, this group appears as a single band showing very 

 little resolution, which terminates sharply on the violet side but 

 shades off gradually toward the red. The effect of pressure is to 

 narrow and intensify the components of the group so that they appear 

 more sharply defined and distinctly separated in the central and short 

 wave-length end of the band, and to narrow the whole band by cutting 

 off or weakening the long wave-length end. In some concentrations, 

 the component of longest wave-length is practically suppressed by 

 pressure. There is also a slight shift of the violet side of this group 

 toward the shorter wave-lengths. In a .2 normal solution a pressure 

 of 1700 atmospheres causes a shift of approximately 5 Angstroms on 

 the violet side of this band and a narrowing of about 20 Angstroms on 

 the red side. 



The double band at wave-length 5200 having a width of about 25 

 Angstroms in a .2 normal solution has its components decidedly 

 sharpened and intensified by the application of a pressure of 1700 

 atmospheres. There also appears to be a very slight shift of the 

 violet side of this band toward the shorter wave-lengths, amounting 

 to 1 or 2 Angstroms, together with a narrowing on the red side of 3 

 or 4 Angstroms. 



The fine blue band at 4272 was made narrower and sharper by 

 pressure and it was also intensified and shifted toward the red, the 

 opposite direction from the shift observed in the case of the red bands. 

 Jones and Strong 8 have described this band as varying in appearance 

 in different solutions, sometimes appearing double and sometimes 

 single. In the more concentrated solutions observed in this work, 

 this band appears double with the dimmer component on the side 

 toward the longer wave-lengths. This component is weakened or 

 caused to disappear by an increase in pressure while the stronger 

 component is sharpened and intensified. The total width of the band 

 in a solution .287 normal at ordinary pressure is about 15 Angstroms. 

 The effect of a pressure of 1500 atmospheres is to narrow the red side 



uncertainties arising from differences in exposure of the plates make exact 

 measurements impossible. 



8 Jones and Strong, Carnegie Publication 130, p. 84. 



