214 REPORT— 1873. 



and chert, many of them symmetrically formed and carefully chipped ; but it 

 seems never to have occurred to them to increase their efficiency by polish- 

 ing them. The still more ancient men of the Breccia have left behind them 

 not even a single bone tool ; their flint implements are rude and massive, 

 show but little attempt at regularity of outline, and are but rudely chipped. 



Report of the Coinmittee, consisting of Dr. Gladstone^ Dr. C. E. A. 

 WrighTj and W. Chandler Roberts, appointed for the purpose of 

 investigating the Chemical Constitution and Optical Properties of 

 Essential Oils. Drawn up Inj Dr. Wright. 



Since the last Meeting of the Association, a number of points connected with 

 the experiments then made have been fully worked out, and some interesting 

 information gained on the subject of isomerism among bodies of the terpene 

 class and their derivatives. 



The action of nitric acid on the terpene of turpentine-oil has been shown 

 by Schwanert to give rise to a non-crystalline acid (ccnnp7i7-esic acid), which 

 is tribasic, and is expressed by the formula Cj^H^^O^ ; the terpene of nutmeg- 

 oil has been found to give rise by similar treatment to oxalic acid, and an 

 acid resembling honey when freshly prepared, but solidifying to a crystalline 

 mass on standing for some months. This has been termed Myristisic acid ; 

 its analysis agrees with the formula C.„,II.,„0,g, 2H,0, the 2H.,0 being lost at 

 100° C, and 6 of the 26 proportions of hydrogen being replaceable by calcium. 

 Simultaneously, toluic and torephthalic acids are prodiiced by the oxidation 

 of the cymeue naturally admixed with the terpene. 



Hesperidene, the terpene of orange-oil, when treated in the same way, gives 

 neither toluic nor terephthalic acid ; oxalic acid, and an acid much resem- 

 bling myristisic acid but containing more oxygen, are formed ; this acid, 

 which has been termed Hesperisic acid, is expressed by the formula C^^H^jO^, 

 2H2O, the 2TL,f> being lost at 100°, and 6 proportions of hydrogen being 

 replaceable by calcium. 



From the character of the oxidation products, it thus seems that the ter- 

 penes of turpentine, nutmeg-oil, and orange-oil are not identical, but only 

 isomeric — a conclusion already drawn from their different physical proper- 

 ties {e.g. their boUiug-points, 160°, 163°-164°, and 178° respectively); 

 turpentine-oil when oxidized also gives rise to smaU quantities of terephthalic 

 acid ; this, however, without doubt arises from the presence of cymene in 

 ordinary tui-pentino {vide infra). 



Although hesperidene contains no cymene ready formed (as proved by the 

 non-formation of toluic and terephthalic acids from it by oxidation, and the 

 failure in extracting cymene by a method which readily yields that hydro- 

 carbon when applied to oil of turpentine or to the mixed hydrocarbons of 

 nutmeg-oU) it is nevertheless closely related to that substance ; by cautiously 

 adding two equivalents of bromine to one of hesperidene, a dibromide is 

 formed (with evolution of heat) : on attempting to distil this product it 

 breaks up into hydrobromic acid and cymene, thus, 



C,„H^,Br, = C,„H,,Er-HHBr=C,„H,,-t-2HBr. 



An intermediate unstable body, Cj„Hjj.Br, appears to be formed ; but three or 

 four distUlations suffice to break up the dibromide almost wholly into cymene 



