608 BI'NSEN MEMORIAL LKCTUKK. 



which he in after life liecanio ii distintiui^^hecl exponent. It consisted 

 of an exact analysis and a detailed description of a specimen of allo- 

 phane from a lionite l)ed near Rf)nn (Pog-g. Ann.. 1884: (31). 53). 



A more specially chemical subject next eno-au'cd his attention, 

 namely, an investigation of a new series of double cyanides, in wiiich 

 he not only determined their composition with exactitude, but siiowed 

 the relationship existinj*' between these and other well-known mem- 

 bers of the same class of bodies. He measured their crystalline form 

 and proved that ammonium ferrocyanide is isomorphous with the cor- 

 responding potassium salt (Pogg. Ann.. 1S35 (34). 131: 1835 (3(1). 4(»4; 

 183« (38), 208). 



All this work was. however, merely of the natui'c of w iiat lie was 

 in the habit of calling "ein kleinei- \'orversnch"" when he was indicat- 

 ing the manner in which a ])ui)il should commence an investigation. 



The Hrst research in which Uunsen showed his power was the clas- 

 sical one on the cacodyl compounds — begun in Cassel in 1837 and con- 

 tinued in Marburg for no less than six years. The piil)lication of this 

 work placed Bunsen at once in the front rank of experinuMitalists. 



To assist in forming an estimate of the scientific value of these 

 researches (Pogg. Ann.. 1837 (4(1). 21U: 1837 (42), 145; Annalen, 1841, 

 (37). 1: 1842 (42), 14; 1843 (46), 1), it may be well to summon to our 

 aid the opinion of a contemporary whom Bunsen himself, as we have 

 seen, considered as a master, both from a philoso])hical and from an 

 experimental pt)int of view, the great Swedish chemist Berzelius. 



Those who have studied his celebrated Jahresbericht will know that 

 Berzelius was unsparing in his criticisiu of inaccurate work and of 

 illogical conclusions. The more valuabl(>. therefore, and reliable are 

 his I'emarks when favorable to the su))j(H-t under review. 



In 1839 (Jahresl)er.. 1839 (18). 487). Berzelius writes: 



"An extremely important discoveiy has been made by Bunsen. in 

 the investigation of the well-known fuming. self-intlaminabl(> licjuid 

 (Cadet's fuming arsenical li([uid) obtained when anhydrous acetate of 

 potash is distilled with arsenious acid. From this body liuns(Mi has 

 prepared several substances whose properties resemble those of an 

 organic compound, in which, however, arsenic enters as an elementary 

 constituent." 



Of the importance of this research as atfectiug chemical th(!ory, 

 Berzelius reports (Jahresber. . 1841 (20), 526): 



In the last German edition of my handbook, I gave what 1 consid- 

 ered the probal)le theoretical views regarding this substance, namely, 

 that it contains the compound radical CjHiaAs.,, similar to the radicals 

 contained in the organic l)odies. for which I have suggested to Bunsen 

 the name " kakodyT in consequence of the nauseous smell of its com- 

 pounds. With regard to this nanie Bunsen writes me as follows: 'The 

 view of the existence of a ternarj' radical Kd^C^HjoAsj agrees so per- 



