242 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



On account of its odour the new element was described 

 (loc. at. p. 341) as BROMINE (Greek, /Spw/xos, a stink). 



Liebig fails to recognise bromine as an element. The 

 German chemist Liebig (1803-1873), in a candid piece of 

 autobiography, wrote in 1838 : 



" I know a chemist who, while at Kreuznach, many years 

 ago, undertook an investigation of the mother-liquor from 

 the salt-works. .He found iodine in it ; he observed, 

 moreover, that the iodide of starch turned of a fiery yellow 

 by standing overnight. The phenomenon struck him ; he 

 procured a large quantity of the mother-liquor, saturated it 

 with chlorine, and obtained by distillation a considerable 

 amount of a liquor colouring starch yellow, and possessing 

 the external properties of chloride of iodine, but differing in 

 many of its reactions from the latter compound. He 

 explained, however, every discrepancy most satisfactorily to 

 himself; he contrived for himself a theory on it." 



" Several months later he received the splendid paper 

 of M. Balard, and, on the very same day, he was in a con- 

 dition to publish a series of experiments on the behaviour 

 of bromine with iron, platinum, and carbon, for Balard's 

 bromine stood in his laboratory, labelled liquid chloride of 

 iodine. Since that time, he makes no more theories unless 

 they are supported and confirmed by unequivocal experi- 

 ments ; and I can positively assert that he has not fared 

 badly by so doing" (Ann. Chem. Pharm., 1838, 25, 29-30; 

 quoted by Hofmann, Trans. C/iem. ^"^.,1875, 28, 1098.) 



D. CYANOGEN. 



Scheele (1782) prepares prussic acid from prussian blue. 

 Prussian blue, or Berlin blue, was first described in 1710, 

 as a product obtained by mixing lixivium sanguinis x with 

 a salt of iron. Scheele, in 1782, distilled both Prussian 

 blue itself and the lixivium from which it was made with 

 vitriolic acid in a glass retort. The distillate was a watery 

 liquor with a "peculiar smell and taste" (Essays^ p. 237). 



1 An extract of calcined blood containing potassium ferrocyanide 



