ON THE CONSTITUTION ETC. OV ESSENTIAL OILS. 319 



In order to add on hydrogen to hesperidenc, this crude hj^driodide ■was 

 heated with phosphorus and water in a scaled tube at 130°-150°. Much 

 phosphine and phosphonium iodide ■were produced, and several times the tubes 

 exploded ; a polymeride of Cj^Hj^,, however, was the sole resulting organic 

 substance. 



The same result was obtained on boiling with phosphorus the crude 

 hydriodide, an inverted condenser being attached. After some time the con- 

 tents of this flask were distilled and found to consist only of C,„H,„ + C,„ 

 Hj„I; the last few drops in the retort boiled at about 250°; boiling alcohol dis- 

 solved the fluid sparingly (cold alcohol dissolved only traces). A few drops of an, 

 oily hydrocarbon deposited on cooling ; on combustion this gave carbon 88-5, 

 hydrogen 11-4 : total 99-9. 



The formula (C^^Hj^ requires carbon 88-2, hydrogen 11-8 ; whence it 

 appears that the hespcridene has become polymerized, the boiling-point being 

 raised about 75°, Gladstone has shown that Cj.H,, polymerides boil near 

 250° ; the analysis indicates rather a subtraction than an addition of hydro- 

 gen, 0,-^23 requiring carbon 88*7, hydrogen 11-3. 



In the hope of obtaining a C^^ acid, the hydriodide was boiled with alcohol 

 and silver cyanide for several hours ; silver iodide was copiously produced, 

 and the liquid acquired a peculiar odour recalling that of the nitriles. 



On boiling with alcoholic potash, ammonia and methylamine were given off, 

 a thick brown carbonized resin was formed, and, in very small quantitj', the 

 potash salt of an acid soluble in ether ; this acid gave a yellowish-white floc- 

 culent precipitate with lead acetate : just sufficient of this lead salt was ob- 

 tained for one determination, which gave lead =o-i-G per cent. Probably 

 this was a basic salt ; the anticipated reactions 



C.„H.e + HI = C.„H,J 



C,„H,J + AgCN = C,„H^„CN+AgI 



C,„H,XI^+2H,0 .... = NH3-HC,„H,„C0,0H 



indicate the formation of an acid, the neutral salt of which would require 

 3G-3 per cent, lead, while the basic salt (C H ) Pb,PbO would require 

 53-7. ' ' 



It is proposed to examine further tlie questions of the synthesis of acids from 

 the different terpenes, by means of the hydrogen chloride or hydrogen bro- 

 mide compounds. 



Appendix. — Since the reading of the above Beport, some further experi- 

 ments have been made on the existence of cymene as a natural constituent 

 of what have been hitherto considered to be pi;re terpenes : by treating 

 such terpenes with sulphuric acid, the C,nIIj„ constituents are polymerized, 

 whilst cymene, if present, is mainly unaltered and can be obtained by dis- 

 tilling the acid liquor in a current of steam. By these means it has been 

 found that the lowest-boiling nutmeg-h3-drocarbon actually does contain 

 cymene ; also that cymene is present in ordinary oil of turpentine ; on the 

 other hand, no trace of cymene is contained in hespcridene, a fact the more 

 remarkable as ])ure cymene is obtainable in quantity by heating the product 

 of the action of bromine on hcsperidenc, viz. Cj,JIjJ]r^, which splits up thus — 



C,„II,3Br,=2IIBr + C,„II,,. 



Apparently the eymeno thus produced, that precontained in nutmeg-oil and 

 oil of turpentine, that derived from camphor and various other varieties now 

 undergoing examination are identical, 



