PROCEEDINGS 



OF 



THE ROYAL SOCIETY, 



December 11, 1884. 



THE TREASURER in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



T. « The Absorption-spectra of the Alkaloids." By W. N. 

 Hartley, F.R.S., Professor of Chemistry, Royal College of 

 Science, Dublin. Received November 19, 1884. 



(Abstract.) 



While studying the molecular constitution of various organic 

 substances by means of their action on the ultra-violet rays in the 

 manner described in the " Philosophical Transactions," vol. 170, 

 p. 257, 1879, it was considered of importance to ascertain whether 

 absolute physical measurements could not be substituted for the 

 uncertain chemical reactions and variable physiological tests at 

 present employed as a means of detecting the alkaloids in medico- 

 legal examinations. About forty alkaloids and derivatives there- 

 from have been examined, authentic specimens having been pro- 

 cured from the chemists by whom they were prepared. Solutions were 

 carefully made of the same strength in most cases, only diactinic 

 solvents, most generally alcohol, being employed. The cells with 

 quartz sides for holding the solutions were of various thicknesses, 

 ranging from 1 mm. to 20 mm. The electrodes employed to give a 

 well-defined spectrum consisted, one of an alloy of tin with 25 per 

 cent, cadmium, the other of lead with cadmium in the same propor- 

 tion. Spectra are thus obtained with lines of the same intensity, 

 numerous and evenly distributed throughout a spectrum extending 



VOL. XXXVIII. B 



