NATURE 



597 



THURSDAY, APRIL 28, 1881 



SCIENTIFIC WORTHIES- 



XVII.— Robert Wilhelm Bunsen 



''T'HE value of a life devoted to original scientific work 

 -*- is measured by the new paths and new fields 

 which such work opens out. In this respect the labours 

 of Robert Wilhelm Bunsen stand second to those of no 

 chemist of his time. Outwardly the existence of such a 

 man, attached, as Bunsen has been from the first, exclu- 

 sively to his science, seems to glide silently on without 

 causes for excitement or stirring incident. His inward 

 life however is on the contrary full of interests and of 

 incidents of even a striking and exciting kind. The dis- 

 covery of a fact which overthrows or remodels our ideas 

 on a whole branch of science ; the experimental proof of 

 a general law hitherto unrecognised ; the employment of 

 a new and happy combination of known facts to effect an 

 invention of general applicability and utility; these are 

 the peaceful victories of the man of science which may 

 well be thought to outweigh the high-sounding achieve- 

 ments of the more public professions. 



Prof. Bunsen is eminently a soldier of science, his 

 devotion to his flag has been unwavering and life-long, 

 and his whole existence has been a noble struggle for the 

 mastery of nature's secrets. Born on March 31, 1811, at 

 Gottingen, where his father was Professor of Theology 

 Bunsen graduated in that ancient University before he 

 had passed through his teens, and published an inaugural 

 dissertation, " Enumeratio ac descriptio hygrometorum." 

 Soon afterwards, at the age of twenty-two, he became a 

 privat-docent at the university of his native town, thus 

 entering the career of a teacher, which he has consistently 

 followed with conspicuous success for close on half a 

 century. In 1836 Bunsen became Professor of Che- 

 mistry at the Polytechnic School in Cassel ; in 1838 

 he was appointed to the Chair of Chemistry in the 

 University of Marburg, where be remained for thirteen 

 years ; afterwards he was for a short time at Breslau, 

 whence he removed to Heidelberg, of which renowned 

 University he has been one of the chief ornaments and 

 attractions for the last thirty years. 



Bunsen' s first scientific investigation was ''one which 

 attracted general attention, and the results of which are 

 of permanent importance. In conjunction with Berthold, 

 a colleague at Gottingen, he showed that moist freshly 

 precipitated ferric hydroxide acts as a certain antidote in 

 cases of poisoning by arsenic, provided that it is exhibited 

 in sufficient quantity and early enough in the history of 

 the case. The explanation of this action is the for- 

 mation of an insoluble ferrous arsenite ; 100 parts of 

 the dry hydroxide carry down from five to six parts 

 of arsenic. So well known and valued is this anti- 

 dote in Germany, that it is kept by apothecaries ready 

 for use. 



In 1835 Bunsen described some singular compounds 

 which the double cyanides form with ammonia. He 

 contradicted the general statement that ammonium 

 ferrocyanide is formed by boiling prussian blue with 

 ammonia ; but showed that it is formed by digesting 

 Vol. XXIII. — No. 600 



lead ferrocyanide with ammonium carbonate. He also 

 measured the angles of crystals of many of the double 

 cyanides. 



In 1837 he struck the first note of one of his most 

 important and fruitful investigations in a memoir on 

 the existence of arsenic as a constituent of organic bodies- 

 In the year 1760 the French chemist Cadet had observed 

 that a mixture of acetate of potash and white arsenic 

 yields, when heated, a heavy brownish-red liquid, which 

 has a frightful smell and fumes strongly in the air, and 

 this liquid was termed Cadet's fuming arsenical liquid. 

 Little more than the fact of its existence was ascertained 

 concerning this body until Bunsen undertook its examina- 

 tion, and in a series of memoirs which have now become 

 classical, and which extended over many years, placed its 

 composition in a true light, thus giving to the world the 

 first member of the now well-known family of the organo- 

 metallic bodies. 



Bunsen showed that Cadet's liquid, as well as its 

 numerous derivatives, contains a radical having the 

 formula C.^H^As, and that this substance in its chemical 

 relations exhibited striking analogies with a metal, being 

 indeed, as he terms it, "a true organic metal." He suc- 

 ceeded in isolating this body, and this discovery formed 

 not only the starting-point for the preparation of hundreds 

 of other similar bodies, but also contributed largely to the 

 development of one of the most important of our chemical 

 theories, that of compound radicals. This body, like 

 most of its compounds, possesses a most offensive odour, 

 so much so that the air of a room containing a trace of 

 the vapour is rendered absolutely unbearable. Hence to 

 this substance Bunsen gave the name of Cacodyl (koki^Sjis, 

 a bad smell). Not only however are these compounds 

 unpleasant, but they are highly poisonous, very volatile, 

 dangerously explosive, and spontaneously inflammable. 

 It is difficult enough nowadays for a chemist to work with 

 such substances armed as he is with a knowledge of the 

 danger which he has to encounter, as also with improved 

 appliances of every kind to assist him in overcoming his 

 difficulties. But Bunsen forty years ago was a traveller 

 in an unknown and treacherous land, without sign-posts to 

 guide him, or more assistance on his journey than was 

 furnished by his own scientific acumen and his unfaltering 

 determination. Nor did he escape scot-free from such a 

 labour, for in analysing the cyanide of cacodyl the com- 

 bustion tube exploded, Bunsen lost the sight of an eye, 

 and for weeks lay between life and death owing to the 

 combined effects of the explosion and the poisonous nature 

 of the vapour. " This substance," he writes, " is extra- 

 ordinarily poisonous, and for this reason its preparation 

 and purification can only be carried on in the open air ; 

 indeed, under these circumstances it is necessaiy for the 

 operator to breathe through a long open tube so as to 

 ensure the inspiration of air free from impregnation with 

 any trace of the vapour of this very volatile compound. 

 If only a few grains of this substance be allowed to 

 evaporate in a room at the ordinary temperature, the 

 eftect upon any one inspiring the air is that of sudden 

 giddiness and insensibility, amounting to complete un- 

 consciousness." 



Taking a totally different direction, Bunsen's next im- 

 portant investigations were concerned with the examina- 

 tion of the chemical changes which occur in the blast- 



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