220 
Proceedings of the Royal Society of Edinburgh. [Sess. 
( O— OH 
{ Q 2 fur die Essigsaure, u.s.w. : 
c-h 3 
sie waren bereits solche, wie sie als s.g. Structurformeln weiter zu ent- 
wickeln und fester zu begrtinden viele Chemiker nachher als eine der ihrer 
Wissenschaft vorzugsweise gestellten Aufgaben betrachteten, viele jetzt 
es thun.” * 
I close this section with an extract from Ernst von Meyer’s Geschichte 
der Chemie von den dltesten Zeiten bis zur Gegenwart, first published in 
1889: — “Ferner legte Couper grossen Nachdruck auf die Fahigkeit der 
Kohlenstoffatome sich unter einander zu vereinigen und zwar so, dass ein 
Theil des ihnen eigenen Bindungsvermogens ausgeglichen wird. Diese 
Vereinigung von Atomen versinnlichte er durch Striche, welche zwischen 
den mit einander verbundenen Theilchen in den chemischen Symbolen 
angebracht wurden, er legte so den Grund zu den sogenannten Structur- 
formeln.” f 
Couper’s Investigations on Salicylic Acid. 
Couper’s second and last experimental investigation was laid before the 
French Academy of Sciences at the meeting of the 7th June 1858. + It 
was entitled “ Recherches sur l’acide salicylique.” He says that he under- 
took this work in order to throw some light on the disputed questions as 
to the constitution and basicity of salicylic acid. This subject had engaged 
Chiozza, who worked at it in Gerhardt’s laboratory, Gerhardt himself, and 
his pupil Drion. Unknown to Couper, Kekule and also Kolbe, along with 
Lautemann, were at the same time occupied with it. Following these 
investigations, which had then for their aim the clearing up of the 
question of the constitution of salicylic acid, we see Gerhardt, Kekule, 
Kolbe, and Couper writing formulae for salicylic acid, and we shall have no 
difficulty in deciding which of these four investigators made the boldest 
and most successful advance in this region. 
In 1852 Chiozza, probably on the suggestion of Gerhardt, examined the 
action of phosphorus pentachloride on gaultheria oil, § at that time the 
usual source of salicylic acid. He found that, on the distillation of the 
product of the reaction, a liquid was obtained which behaved like an 
acichloride, giving chlorobenzoic acid on treatment with water. 
* Page 829. t Page 270. 
I Cornptes rendus , xlvi. 1107-1110. 
§ Ibid., xxxiv. 850-851, seance dn lundi, 31 May 1852. 
