102 



REPORT — 1902. 



The absorption spectra of aqueous solutions of all the specimens of 

 phloroglucinol described above were photographed, and, on comparison, 

 found to be identical. The measurements were actually taken and the 

 curve drawn from the photographs of the specimen prepared from resorcin 

 and purified by Skraup's method. 



A layer 50 mm. thick of a solution containing 1 milligram molecule in 



Curves of Molecular Vlbralio7is. — ^(1) Phloroglucinol; (2) Trimethylphloroglucinol. 



20 c.c water absorbs all rays beyond ^j\ 3323 (\=3009), while a layer 

 5 mm. thick of the same solution absorbs all rays beyond ^ IX 3568 

 (\=2802). 



The absorption band is not strongly marked : it appears first in the layer 

 1 mm. thickfof the'^solution containing 1 milligram-molecule in 20 c.c. 

 water, and nearly dies out in the layer 2 mm. thick of the solution con- 

 taining 1 milligram-molecule in 100 c.c, although its position is still 

 distinctly traceable by the weakness of the spectra in solutions of greater 



