2G6 ROSACEiE. 



Bulgaria experience shows that the oil of the mountain districts holds 

 a larger proportion of stearoptene than that of the lowlands. 



Turkish oil of rose is stated by Baur to deviate a ray of polarized 

 light 4° to the right, when examined in a column of 100 mm. The oil 

 from English roses which we examined exhibited no rotation. 



Chemical Composition — Bose oil is a mixture of a liquid con- 

 stituent containing oxygen, to which it owes its perfume, and the solid 

 hydrocarbon or stearoptene already mentioned, which is entirely desti- 

 tute of odour. The proportion which these bodies bear to each other 

 is extremely variable. From the Turkish oil, it may be obtained to the 

 extent of 18 per cent., and from French and English to 35, 42, 60 or 

 even 68 per cent. 



Though the stearoptene can be entirely freed from the oxygenated 

 oil, no method is known for the complete isolation of the latter. As 

 obtained by Gladstone,^ it had a sp. gr. of 0*881 and a boiling point of 

 216° C. 



With regard to the stearoptene of rose oil, the analyses of Theodore 

 de Saussure (1820) and Blanchet (1833) long since showed its com- 

 position to accord with the formula C"H-^ The experiments of one of 

 us ^ confirm this striking fact, which assigns to the stearoptene in 

 question a very exceptional place among the hydrocarbons of volatile 

 oils, all of which are less rich in hydrogen. 



Rose stearoptene separates when attar of roses is mixed with alcohol. 

 We have isolated it also from oil obtained from Mitcham roses, by 

 diluting the oil with a little chloroform and precipitating with glacial 

 acetic acid or spirit of wine, the process being several times repeated. The 

 stearoptene was lastly maintained for some days at 100° C. ; thus 

 obtained, it is inodorous, but when heated evolves an offensive smell 

 like that of heated wax or fat. At 32"5° it melts; at 150° vapour is 

 evolved ; at 272° C. it begins to boil, soon after which it turns brown 

 and then blackish. Stains of the stearoptene on paper do not disappear 

 by the heat of the waterbath and the relapse of some days. 



If cautiously melted by the warmth of the sun, the stearoptene forms 

 on cooling microscopic crystals of very peculiar shape. Most of them 

 have the form of truncated hexahedral pyramids, not however belonging 

 to the rhombohedric system, as the angles are evidently not equal ; 

 many of them are oddly curved, thus §. Examined under the polarizing 

 microscope, these crystals from their refractive power make a brilliant 

 object. 



Rose stearoptene is a very stable body, yet by boiling it for some 

 days with. fuming nitric acid, it is slowly dissolved, and converted into 

 various acids of the homologous series of fatty acids, and into oxalic 

 acid. Among the former, we detected butyric and valerianic. The 

 chief product is however succinic acid, which we obtained in pure 

 crystals, showing all the well-known reactions. 



The same products are obtained even much easier by treating 

 paraffin with nitric acid ; it yields however less of succinic acid. The 

 general behaviour and appearance of paraffin is in fact nearly the same 

 as that of rose stearoptene. But what is called imro^w, is a series of 

 extremely similar hydrocarbons, answering to the general formula 



1 Journ. of Chem. Soc. x. (1872) 12. ^ piuckiger, Pharm. Journ. x. (1869) 147. 



