6 H. N. MOSELEV. 



observed by viewing the spectrum with the bright sodium 

 line in the field. The second, situated between D and E, is 

 most intense on its least refrangible border, and shades off 

 towards the violet. The third band is a broad, dim one, 

 stretching from h to F. Very little of the red end of the 

 spectrum is cut off. The whole of the violet is absorbed. 

 In very intense solutions (PI. I, fig. 46) the absorption at 

 the violet end spreads up to 6, and unites with the third 

 band, so that the light is entirely cut off up to h, where 

 there is a defined dark edge. The second band is intensi- 

 fied and becomes black. The first band is black as before, 

 but a paler band is added to it in continuation on its red 

 side. In very intense solutions the two principal bands 

 broaden out and almost run together, being separated only by 

 a narrow interval of yellow. The two principal bands coincide 

 very nearly with those of turacin. The only difference is 

 that the least refrangible band in turacin extends a little 

 further to the green side of D than does that of Pentacrinin. 

 On the acid alcoholic solution being rendered alkaline by 

 addition of ammonia the solution becomes of a bluish-green 

 colour, which shows a slight red fluorescence on the concen- 

 tration of sunlight in it. 



The spectrum is changed. An intensely black band now 

 occupies a space to the less refrangible side of B ; to the red 

 side of D is a broad pale band, whilst the third band between 

 h and F remains as before, excepting that it is intensified for 

 rather more than half its breadth on its violet side (PL I, 

 fig. 5 c). In very weak solutions the first and third bands 

 remain visible after the middle one is lost. 



The solution can be rendered acid or alkaline any number 

 of times with corresponding change of colour and spectrum. 

 By careful addition of ammonia in small quantities to the 

 acid solution, in a tall vessel, one part of the solution can be 

 obtained green, whilst the remainder is still red. 



Thus the passage of one spectrum into the other may be 

 seen at the junction of the two solutions. As the least re- 

 frangible band of the acid spectrum fades, it takes the form 

 of a fine black line to the red side of D, with a fainter 

 margin extending just over D towards the green. As the 

 ammoniacal portion of the solution is approached a dark, 

 broad band is seen to extend gradually towards the red from 

 the least refrangible acid band up to the position of the least 

 refrangible margin of the dark alkaline band in the extreme 

 red. The least refrangible margin of the broad band darkens 

 as the least refrangible acid band fades from view, and at 

 length assumes the full intensity of the least refrangible alka- 



