20 EEPOBi — 1887. 



describes the condition of organic chemistry as one enough to drive a man 

 mad. ' It seems to me,' says he, ' like the tropical forest primaeval, full of 

 the strangest growths, an endless and pathless thicket in which a man 

 may well dread to wander.' Still clearances had already been made in 

 this wilderness of facts. Berzelius in 1832 welcomed the results of Liebig 

 and Wohler's research on benzoic acid as the dawn of a new era ; and such 

 it really was, inasmuch as it introduced a novel and fruitful idea, namely 

 the possibility of a group of atoms acting like an element by pointing out 

 the existence of organic radicals. This theory was strengthened and con- 

 firmed by Bunsen's classical researches on the cacodyl compounds, in 

 which he showed that a common group of elements, which acts exactly as 

 a metal, can exist in the free state, and this was followed soon afterwards 

 by isolation of the so-called alcohol radicals by Frankland and Kolbe. It 

 is however, to Scborlemmer that we owe our knowledge of the true con- 

 stitution of these bodies, a matter which proved to be of vital importance 

 for the further development of the science. 



Turning our glance in another direction we find that Dumas, in 1834, 

 by his law of substitution threw light upon a whole series of singular 

 and unexplained phenomena by showing that an exchange can take place 

 between the constituent atoms in a molecule. Laurent indeed went 

 farther, and assumed that a chlorine atom, for example, took up the posi- 

 tion vacated by an atom of hydrogen and played the part of its displaced 

 rival, so that the chemical and physical properties of the substitution- 

 prodiTct were thought to remain substantially the same as those of the 

 orio-inal body. A singular story is connected with this discovery. At a 

 soiree in the Tuileries in the time of Charles X. the guests were almost 

 suffocated by acrid vapours which were evidently emitted by the burning 

 wax candles, and the gi'eat chemist Dumas was called in to examine into 

 the cause of the annoyance. He found that the wax of which the candles 

 were made had been bleached by chlorine, that a replacement of some of 

 the hydrogen atoms of the wax by chlorine had occurred, and that the 

 suffocating vapours consisted of hydrochloric acid given off daring the 

 combustion. The wax was as white and as odourless as before, and the 

 fact of the substitution of chlorine for hydrogen could only be recognised 

 when the candles were destroyed by burning. This incident induced 

 Dumas to investigate more closely this class of jihenomena, and the re- 

 sults of this investigation are embodied in his law of substitution. So 

 far indeed did the interest of the French school of chemists lead them that 

 some assumed that not only the hydrogen but also the carbon of organic 

 bodies could be replaced by substitution. Against this idea Liebig 

 protested, and in a satirical vein he informs the chemical pubKc, 

 writing from Paris under the nom de plume of S. Windier, that he has 

 succeeded in substituting not only the hydrogen but the oxygen and 

 carbon in cotton cloth by chlorine, and he adds that the London shops 

 are now selling nightcaps and other articles of apparel made entirely of 

 chlorine, goods which meet with much favour, esi)ccially for hospital use ! 



