SKETCH OF ROBERT WILHELM BUN SEN. 551 



double cyanides form with ammonia, and the crystals of many of the 

 double cyanides. In 1837 he began a series of investigations of the 

 liquid called Cadet's fuming arsenical liquid the product of heating 

 a mixture of acetate of potash and white arsenic, discovered in 1760 

 and brought out the radicle cacodyl, the first of a series of organo- 

 metallic compounds which exhibit striking analogies with the metals. 

 These bodies are unpleasant in every way, extremely poisonous, dan- 

 gerously explosive, highly inflammable, and often, like cacodyl, insuf- 

 ferably offensive in odor. " It is difiicult enough nowadays," says Pro- 

 fessor Roscoe, in " Nature," " for a chemist to work with such sub- 

 stances, 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 traveler 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 labor, for, in analyzing the cyanide of 

 cacodyl, the combustion-tube exploded, Bunsen lost the sight of an 

 eye, and for weeks lay between life and death, owing to the com- 

 bined effects of the explosion and the poisonous nature of the vapor. 

 * This substance,' he writes, ' is extraordinarily poisonous, and for this 

 reason its preparation and purification can only be carried on in the 

 open air ; indeed, under these circumstances, it is necessary for the 

 operator to breathe through a long open tube so as to insure the inspi- 

 ration of air free from impregnation with any trace of the vapor 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 

 effect upon any one inspiring the air is that of sudden giddiness and 

 insensibility, amounting to complete unconsciousness.' " 



His next research, published in 1838, was into the chemical changes 

 which occur in the blast-furnace. In it he showed that at least forty- 

 two per cent, of the heat evolved from the fuel employed in the fur- 

 nace was lost, and pointed out that a great economy might be effected 

 by collecting the combustible gases which escaped, and saving them 

 for subsequent use. The investigation led to the introduction of im- 

 proved methods by which the waste gases were utilized, and the cost 

 of the manufacture of iron was cheapened. The experiments made in 

 this research were the first in which an accurate method of gas-analysis 

 was employed, and entitle Bunsen to the credit of having introduced 

 new and valuable processes in that line to chemistry. 



In 1841 he invented the Bunsen battery, an apparatus which has 

 come into general use as a scientific instrument, and in telegraphy. 

 Its chief peculiarity is the substitution of carbon for copper or plati- 

 num as the negative pole. 



He visited Iceland in 1846-'47, and devoted special attention to the 

 study of the volcanic phenomena of the island, particularly of the 



