176 Obituary Notices of Fellows deceased. 



Liebig. This great success caused other Universities to adopt the 

 system of Liebig, so that about the middle of the century many of the 

 German Universities were provided with public laboratories. One of 

 the best of these existed at Marburg, under the direction of Prof. 

 Bunsen. Maxwell Simpson decided to go there and learn the 

 Continental system of teaching the science of chemistry. The authori- 

 ties of the Medical School in St. Peter's Street gave him leave of 

 absence for three years, and he, with his whole family, left for Marburg 

 in the spring of 1851. At Marburg a great disappointment awaited 

 him. Prof. Bunsen had accepted a call to Breslau and had just left 

 Marburg. His successor at the University, Prof. Kolbe, enjoyed a 

 considerable reputation as a chemist, which induced Simpson to remain 

 at Marburg till 1853. He then went to Heidelberg, where, in the 

 meantime, Bunsen had accepted the Chair of Chemistry. At Heidelberg 

 Simpson did his first original work. 



Nitrogen in organic compounds was at the time usually determined 

 according to the method of Will and Varrentrapp. This method is 

 not applicable to cyanides and certain amides. The methods of Liebig 

 and Dumas are not reliable when the compounds under examination 

 are difficult to burn. The problem, to discover a method which 

 could be used in all cases, remained to be solved. Simpson discovered 

 such a method in Bunsen's laboratory. 



His method is based on the same principles as those of Liebig and 

 Dumas, but differs from theirs by the form of the apparatus, the use of 

 mercuric oxide in place of cupric oxide, and the measurement of the 

 gas over mercury instead of over water. ("Jour. Chem. Soc.,"vi, 289.) 



Fifty years have passed since the introduction of this method; 

 other methods have since been recommended, but none more accurate 

 or reliable than Simpson's. In 1854 he returned to Dublin, and took 

 up again his lectures at St. Peter's Street School of Medicine. He 

 discharged these duties till the end of the session, in 1856, when he 

 finally gave up his lectureship, and proceeded with his family to 

 Paris and commenced to work there in Wurtz's laboratory. 



As early as 1843 it was recognised that the atoms of different 

 elements are not of the same chemical value. Two atoms of chlorine 

 were called an equivalent of chlorine, two atoms of aluminium three 

 equivalents of aluminium. The chemical value of the oxygen atom 

 used to be taken as the unit. As the knowledge of compound 

 organic radicals was still in its infancy, their valency was not taken 

 into consideration. The formulae of the acids represented equivalent 

 quantities, viz., such quantities of different acids as would neutralise 

 the same quantity of a base. 



As examples may be given the formulae which Berzelius gave to 

 acetic, tartaric, and citric acids : 



