ALAX R . ALRRIGHT AND CHARLES 0 . YOUKG.
2382
this, but it :,eemed best to replace the I I O volt current in the control circuit, and in accordance with the suggestion a t the end of my note 1 supra) d M‘cstinghousc bell-ringing transformer was connected with its priman acruss the main supply, and the relay and thermoregulator operating on the outside 2 4 v. sccondary terminals. This arrangement givcu practicdlq DCJ iiouble, and i.- dt present used on the large incubator described, on three gas-healed \later baths, using the Beans electromagnetic gas valve; and on a large electrically heated air-current drier, taking about 30 amperes in the heating circuit; in the latter case, the LOO ohm relay operating 011 the 24 v. circuit controls a branch of the t LC) circuit which operates a large motor-starting relay i”Contactor”), tile coil ot which takes 0.4 ampere. ‘Cwo different makes of these contactors arc at present in satisfactory use in this Institute, one A. C., and the other I).c‘, ‘l’hey arc rather clumsy for handling currents of less than 1 5 amperes, and there would appear to be some demand in laboratories for a well-constriicted relay operating on I I O v. A. C. or D. C., to control circuits cdrrying from 2 to r L j ampcres--such relays do not appear to be made at present; ‘the ordinary main line relaq will usually take care of 2 amperes, though the lead t o the armature may warm up a little. I believe that the lower voltage a t the break i i a decided advantage; the little bell-ringing transformers take very little current, and one will operate a large number ol such temperature-control circuits. F. ALEX. MCDERMOTT t,.
LIIBLLON JWTITUTB, U N I V R R S W Y OF PITTSXiURGH PfTTSRTIRClI
’r 1
THE DETERMINATION OF VOLATILE ESTERS IN CITRUS OILS AND EXTRACTS. BY -&LAN
K ALBRIGHT AND
CHARLES
0. Y O U N G
Received August 14, 1915.
I. Theoretical.--The citrus oils have been shown, by a large number of investigators, to be very complex mixtures, as is true of practically all of the volatile oils. The principal representatives of the class, lemon and orange oils, are very similar in composition Each contains over 90:& of hydrocarbons, the terpene d-limonene being in preponderance. Aldehydes constitute about 4-67’ of lemon oil, about I-3% of orange oil. Citral is the most important member of this group present, but is accompanied by smaller proportions of citronellal and other aliphatic members such as nonyl and decyl aldehydes. A number of other substances are present, to which some of the finer characteristics of the odors of the oils are due. The most important of these are theesters, the identity of which has been fixed as linalyl and geranyl acetates2 “The Volatile Oils,’’by Gildemeister Sr Hoffman 1 m n a m d Swintoii. Phu?nz .r 61, rgG 370 i i S 9 8 ,
VOLATILE ESTERS IN CITRUS OILS AND EXTRACTS.
2383
Fairly satisfactory methods have been elaborated for the examination of the oils, in so far as regards the physical properties and the aldehyde content, but we have thought that a knowledge of the proportion of esters present would be an aid in forming judgment of these oils. In regard to lemon oil, some work has already been done in this field, and the following data are available: Unmey and Swinton‘ report on an examination of lemon oil, giving an account of a process which involves the distillation of the terpenes in vucwo, removal of the aldehydes from the remaining oil by means of sodium acid sulfite, saponification, and fractional distillation to isolate the alcohols. The statement is made that pure oils contain from I . z to I .4% of esters, calculated as geranyl acetate. We consider the process to be too involved to be a generally useful method of examination, and believe the quantitative separation of the aldehydes by the acid sulfite method to be practically impossible. Bert6 states that the saponification number of the evaporation residue of a lemon oil should not exceed “3.5%,” a higher figure indicating added fats.2 A. Parrozzani3 has recently published the results of some examinations of “terpeneless” lemon oils. The “ terpene-free” oils are distilled with steam, and the aldehydes removed from the distilled oil with acid sulfite, but beyond these statements nothing is said regarding the procedure followed in the ester determination. Parrozzani gives the ester content of five of these concentrated oils, the range being from 26.1% to 37.2%, calculated as linalyl acetate. He believes that the ratio between the ester and the aldehyde content should be useful in judging a terpeneless oil. 11. Material.-The material upon which our experimental work was done consisted, first, of mixtures of known composition, which were made up as follows: lindyl acetate 2.5%, citral 470, limonene 93.5% “ “ 2 .o 4 94.0 ‘I “ 4 94.5 ‘, I .o “ 4 95.o , (5) 0.5 4 95.5
(I)
;; ::
(1
(2)
I’
The linalyl acetate, obtained from Fritzsche Bros., had been stored under conditions favorable to its preservation. It showed an ester content of 85.37& The citral was a fresh sample, purchased from Fritzsche cit. Boll. chim. farm., 43, 709; through Chew Zentr., 1904, 11, 1670. The exact meaning of the term “3.5%” is not stated in the abstract. The original has not as yet become available. * A n n . R . Stae. Sfierim. Acireale., 2, 86 (1914); abstract J . SOC. c k m . ind., 34, LOG.
a
301.
2384
M A N R. .1LBRIGHT AND CHARLES 0 . I’OUh’G.
Rros. The limonene was obtained from lemon oils by fractional distillaw,and if. had ari apparent ester content, after rulntcd a. linaiyl acetate. Considering the nene remains ili the saniple aitcr the iracji this amcmrit. oi saponifiable matter on the i:i r - i t r . ~i i ~l i i i . r:!ixt.iircL ~r?;ictei i ! ~ wit11 these t:.r!:cnes is Finrther, cxperimmtal nark \vas t-lone iipcin samples of Sicilian lemon aind X ~ . J Esome samplei 1-11terpene. p:irtt!: (-Gxiiriicrciali?- inad(.. partly prepared ir, the cm oi T-olatilt. wter?, the authors
hung in a hemispherical i.: ~ a ~ u ~ oi ft i2 i- j rnm.! repil:lti-td t o qi rc a slmv ratc: of dktiliation. per ininutcj. m~:I[iie pr:)cr.;.; not rliiturheg-i ceases 1-0 comc over. When the automatic stopping of tlie vacuum distillation has taken the 1iask i. connwted with ;I. long condenser. and a current of steam through until tlic T o!unie of the distillate reaches m o cc. This cktillatioi; i 5 w regulated i t s to wnsunie at least -15 minutes. T h e \vA~iineof material in the Bask i s kept :is nearly constant as possible by heating with a flame. ‘i5’i1cn the cteam tlisti!lation is carried out in less tinit- t.fiaii this. i L i;: ahnoit iti\-ariably iound that a sufficient limount of les.; readiiy i.oiatil.-. 1nateri:ri i.: c!riT;m i”:ei- t:) produce murkiness: and to -io~sIy-with the tit,ratiori. ’ h e same effect i$ observed when thc \-ciltLmc o f oil \vith Tf-ater in t?1
